Intermediates for the production of epipodophylotoxin and related compounds and processes for the preparation and use thereof

ABSTRACT

There is provided a novel and efficient stereoselective total synthesis of epipodophyllotoxin and related epipodophyllotoxin compounds of the general formula ##STR1## wherein R 1  and R 2  each are independently hydrogen or (lower)alkoxy, or R 1  and R 2 , taken together, is methylenedioxy; R 4  and R 6  each are independently hydrogen or (lower)alkoxy; and R 5  is hydrogen or a phenol-protecting group; or an acid addition salt thereof. The present invention also provides novel intermediates and processes for the preparation of said intermediates, which are then converted into known antineoplastic agents.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of our prior, co-pending applicationSer. No. 722,932, filed Apr. 12, 1985, now U.S. Pat. No. 4,644,072.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to intermediates which can beconverted into epipodophyllotoxin and related antineoplastic agents.More specifically, this invention relates to new and efficient totalsynthesis of epipodophyllotoxin, which can then be readily converted byknown procedures into known antineoplasitc agents. Additionally, thepresent invention provides processes for the preparation of suchintermediates, and processes for the conversion of the intermediatesinto epipodophyllotoxin and related compounds.

2. Disclosure Statement

Epipopohyllotoxin (I) is the 4-hydroxy epimer of podophyllotoxin (II),which is a known lignan lactone isolated from several species ofPodophyllum and possesses potent cytotoxic activity. Numerous otherrelated compounds having the characteristic aryltetralin ring structure,either naturally occurring or derived from some naturally occurringcompounds are known; some of these compounds possess antineoplasticactivity, while others are useful for the conversion to compounds havingsuch activity. Epipodophyllotoxin (I) and podophyllotoxin (II) have thestructures shown below. ##STR2## Many of these compounds, includingpodophyllotoxin, have now been prepared by total synthesis.

In J. Org. Chem., 31, 4004-4008 (1966), W. J. Gensler and C. D. Gatsonisdescribe the completion of the total synthesis of podophyllotoxin (II)through the epimerization by enolate quenching of theO-tetrahydropyranyl derivative of picropodopyllin. However, thisepimerization does not proceed to completion, and separation of an about45:55 mixture of podophyllotoxin (II) and picropodophyllin (III) isrequired. Picropodophyllin (III) which is the cis-lactone isomer ofpodophyllotoxin (II) has the structure: ##STR3##

In J. Am. Chem. Soc., 82, 1714-1727 (1960), W. J. Gensler et al. reportthe total synthesis of picropodophyllin (III) by a lengthy procedureinvolving 13 steps and a low overall yield. The present invention iscompletely different from that reported by Gensler et al. and avoidsaltogether the preparation of picropodophyllin (III).

In J. Org. Chem., 46, 2826-2828 (1981), A. S. Kende et al. report on animproved total synthesis of podophyllotoxin (II) in 12 steps with anoverall yield of 4.5% from piperonal. However, the Kende synthesisrequires the preparation and then the subsequent epimerization ofpicropodophyllin (III) similar to the above-mentioned Gensler synthesis.

In J. C. S. Perkin I, 271-276 (1982), W. S. Murphy and S. Wattanasindescribe an improved synthesis of the aryltetralone (IV) having thestructure ##STR4## The aryltetralone (IV) is an intermediate in thesynthesis of picropodophyllin (III), which is described above in J. Am.Chem. Soc., 82, 1714-1727 (1960). The present invention also utilizesthe aryltetralone (IV) as a starting material in the total synthesis ofepipodophyllotoxin (I) described herein.

In J. Am. Chem. Soc., 103, 6208-6209 (1981), D. Rajapaksa and R. Rodrigoand in J. Org. Chem., 45, 4538-4540 (1980), R. Rodrigo, report a newsynthesis of podophyllotoxin (II) and epipodophyllotoxin (I) whichavoids the thermodynamic hurdle present in the conversion ofpicropodophyllin (III) to podophyllotoxin (II) as was previouslydescribed in the above-mentioned references of Gensler et al. and Kendeet al. However, the Rodrigo synthesis requires the preparation of abicyclic precursor (compound 9 in the 1980 reference), and asatisfactory yield can be achieved only by recycling procedures.

The present invention also avoids the picropodophyllin (III)intermediate and, in addition, provides a new and efficientstereospecific synthesis utilizing inexpensive chemicals, such that thenew process described herein is commercially feasible.

U.S. Pat. No. 3,524,844, issued Aug. 18, 1970 to Keller-Juslen et al.describes the preparation of4'-demethylepipodophyllotoxin-β-D-(substituted)glucosides of the formula##STR5## wherein, inter alia, R¹ is methyl (etoposide) or 2-thienyl(teniposide) from 4'-demethylepipodophyllotoxin (V) having the structure##STR6## which, in turn, is prepared from podophyllotoxin (II). The4'-demethylepipodophyllotoxin-β-D-(substituted)glucosides, andespecially etoposide (R¹ =methyl) and teniposide (R¹ =2-thienyl), areantineoplastic agents which are useful in the treatment of humancancers, especially testicular cancer.

SUMMARY OF THE INVENTION

The present invention provides an efficient and stereospecific totalsynthesis of epipodophyllotoxin (I) and related compounds which canreadily be converted into known antineoplastic agents. Accordingly,there are provided novel intermediates having the formulae depicted inScheme 1. ##STR7## wherein R¹ and R² each are independently hydrogen or(lower)alkoxy, or R¹ and R², taken together, is methylenedioxy; R³ ishydrogen or a carboxyl-protecting group; R⁴ and R⁶ each areindependently hydrogen or (lower)alkoxy; R⁵ is hydrogen or aphenol-protecting group; R⁷ is hydrogen, halogen (lower)alkoxycarbonyl,carboxyl, cyano, trimethylsilyl, phenylsulfonyl or phenoxycarbonyl inwhich the phenyl ring of R⁷ may contain one or two substitutentsindependently selected from (lower)alkyl, halogen, (lower)alkoxy andtrifluoromethyl; and R⁸ is cyano, aminomethyl, formyl or carbamoyl; oran acid addition salt thereof.

In another aspect of the present invention, there is provided anefficient and improved synthesis of the aryltetralones VI from the novelintermediates XIV which can be optionally isolated and having theformula depicted in Scheme 2. ##STR8## wherein R¹, R², R³, R⁴, R⁵ and R⁶are as previously defined; and R⁹ is phenyl or (lower)alkyl optionallysubstituted by one or more halogen atoms selected from fluorine,chlorine and bromine.

The present invention also provides stereoselective processes for thepreparation of intermediates in the total synthesis ofepipodophyllotoxin and epipodophyllotoxin related derivatives. Use ofthe intermediates and processes of the present invention avoids thedifficulties encountered in the prior art and provides a commerciallyfeasible synthesis for useful antineoplastic agents such as etoposideand teniposide.

The terms "(lower)alkyl" and "(lower)alkoxy" as used herein and in theclaims (unless the context indicates otherwise) mean unbranched orbranched chain alkyl or alkoxy groups containing from 1 to 6 carbonatoms such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl,t-butyl, amyl, hexyl, etc. Preferably, these groups contain from 1 to 4carbon atoms and, most preferably, they contain 1 or 2 carbon atoms.Unless otherwise specified in the particular instance, the term"halogen" as used herein and in the claims is intended to includechlorine, fluorine, bromine and iodine. The term "acid addition salt" isintended to include the nontoxic carboxylic and phenolic acid salts,e.g. nontoxic metallic salts such as sodium, potassium, calcium andmagnesium, the ammonium salt and salts with nontoxic amines, e.g.trialkylamines, procaine, dibenzylamine, pyridine, N-methylmorpholine,N-methylpiperidine and other amines which have been used to form saltsof carboxylic acid and phenols.

As the compounds of the present invention may possess one or moreasymmetric carbon atoms, the invention includes all of the possibleenantiomeric and diastereomeric forms of the compounds of the generalformulae depicted in Schemes 1 and 2 and in the claims. Mixtures ofisomers can be separated into individual isomers according to methodswhich are known per se, e.g. fractional crystallization, adsorptionchromatography or other suitable separation processes. Resultingracemates can be separated into antipodes in the usual manner afterintroduction of suitable salt-forming groupings, e.g. by forming amixture of diastereoisomeric salts with optically active salt-formingagents, separating the mixture into diastereomeric salts and convertingthe separated salts into the free compounds. The possible enantimericforms may also be separated by fractionation through optically activehigh pressure liquid chromatography columns.

It it is desired to prepare the natural (-) isomer ofepipodophyllotoxin, then the synthetic (+) isomer of the presentinvention may be resolved by resolution methods well-known to thoseskilled in the art. Alternatively, the resolution may be effected at anearlier stage in the synthesis by the same general methods with one ofthe intermediates described herein which is capable of forming anoptically active salt to produce the desired optically active (+) or (-)isomer of epipodophyllotoxin. As an example of a resolution procedure inthis general class of compounds, W. J. Gensler et al. in J. Am. Chem.Soc., 82, 1714-1727 (1960) described the resolution ofDL-α-apopodophyllic acid to the natural optically activeα-apopodophyllic acid by forming and isolating the correspondingoptically active quinine salt.

Carboxyl-protecting groups which can be employed in the presentinvention to block or protect the carboxylic acid function arewell-known to those skilled in the art and include moieties such as(lower)alkyl, phenyl(lower)alkyl, ring substituted phenyl(lower)alkyl,methoxymethyl, benzyloxymethyl, allyl, diphenylmethyl and the like.Phenol-protecting groups which can be employed in the present inventionto block or protect the phenol function are also well-known to thoseskilled in the art and include moieties such as (lower)alkyl,phenyl(lower)alkyl, ring substituted phenyl(lower)alkyl,benzyloxycarbonyl, 2,2,2-trichloroethoxycarbonyl, methoxymethyl, allyland the like. Other suitable protecting groups are disclosed in"Protective Groups in Organic Synthesis", Theodora W. Greene (John Wiley& Sons, 1981), Chapter 3 for phenol and Chapter 5 for carboxyl, whichare hereby incorporated by reference.

DESCRIPTION OF THE INVENTION

According to one aspect of the present invention, there are providedcompounds of the formula ##STR9## wherein R¹ and R² each areindependently hydrogen or (lower)alkoxy, or R¹ and R², taken together,is methylenedioxy; R³ is hydrogen or a carboxyl-protecting group; R⁴ andR⁶ each are independently hydrogen or (lower)alkoxy; and R⁵ is hydrogenor a phenol-protecting group; or an acid addition salt thereof.

In a preferred embodiment, there are provided compounds of the formula##STR10## wherein R³ is hydrogen or a carboxyl-protecting group, and R⁵is hydrogen or a phenol-protecting group; or an acid addition saltthereof.

In another preferred embodiment, there are provided compounds of theformula ##STR11## wherein R³ is hydrogen or a carboxyl-protecting group,and R⁵ is hydrogen or a phenol-protecting group; or an acid additionsalt thereof.

In the compounds of Formulae VIIIa and IXa, R³ preferably is hydrogen,(lower)alkyl, phenyl(lower)alkyl, ring substituted phenyl(lower)alkyl ordiphenylmethyl and, most preferably, is (lower)alkyl or diphenylmethyl.R⁵ preferably is hydrogen, (lower)alkyl, phenyl(lower)alkyl, ringsubstituted phenyl(lower)alkyl, benzyloxycarbonyl or2,2,2-trichloroethoxycarbonyl and, most preferably, is methyl or benzyl.The phenyl ring of R³ and R⁵ may contain one or two substituentsindependently selected from (lower)alkyl, halogen, (lower)alkoxy andtrifluoromethyl.

The compounds of Formula VIII may be prepared from the correspondingaryltetralomes of the Formula VI by reduction of the ketone radical incompounds VI or VIa and subsequent dehydration of the resulting alcoholsVII or VIIa by methods well-known to those skilled in the art, as shownin Scheme 3. ##STR12## wherein R¹, R², R³, R⁴, R⁵ and R⁶ are aspreviously defined.

The aryltetralone starting material of the Formula VI wherein R¹ and R²,taken together, is methylenedioxy, R³ is hydrogen, CH₃ or C₂ H₅, R⁴ andR⁶ are methoxy, and R⁵ is methyl may be prepared by the general methoddescribed in J. Am. Chem. Soc., 82, 1714-1727 (1960), W. J. Gensler etal. Starting materials of Formula VI may also be prepared by an improvedprocedure described in J. C. S. Perkin I, 271-276 (1982), W. S. Murphyand S. Wattanasin, in which R¹ is methoxy and R² is hydrogen, or R¹ andR², taken together, is methylenedioxy, R³ is hydrogen or ethyl, R⁴ andR⁶ are hydrogen or R⁴ and R⁶ are methoxy, and R⁵ is methyl.Alternatively, the starting materials of the general Formula VI may beprepared by the new and improved procedure illustrated in more detail inthe disclosure and examples of the present invention.

According to one reaction route, when it is desired to change the R³carboxyl-protecting group, the aryltetralone VI is first hydrolyzed byconventional methods, such as acid or base hydrolysis, and preferably bybase hydrolysis, for example, potassium hydroxide. The resulting acidVIa is then subjected to selective reducing conditions to effect thereduction of the ketone radical to the alcohol VIIa. The reduction maybe accomplished by catalytic hydrogenation employing hydrogenationcatalysts such as palladium, platinum, Raney nickel or ruthenium, beingoptionally supported on a conventional carrier such as carbon,diatomaceous earth, etc., in non-reducible inert solvents such as water,methanol, ethanol or ethyl acetate. Hydrogenation is preferablyconducted at room temperature and at atmospheric or slightly elevatedpressure. More preferably, the aryltetralone VIa is reduced in asuitable solvent with a selective reducing agent, e.g., sodiumborohydride, sodium cyanoborohydride, zinc borohydride, sulfuratedsodium borohydride (NaBH₂ S₃), lithium borohydride, disiamylborane,ammonia borane, t-butylamine borane, pyridine borane, lithiumtri-s-butylborohydride, or other similar reducing agents which will notreduce the carboxylic acid radical. The alcohol VIIa which is producedis then subjected to standard dehydration conditions with a small amountof organic or mineral acid such as p-toluenesulfonic acid or sulfuricacid to give the trans-olefin VIII, wherein R³ is hydrogen. The reactionis carried out in a suitable inert organic solvent, e.g., toluene,benzene, ether or methylene chloride, in the presence of a drying agent,e.g. Na₂ SO₄, molecular sieves, etc., or preferably, the water which isproduced is azeotropically removed with a Dean-Stark trap or similarapparatus. The trans-olefin VIII, wherein R³ is hydrogen, may then beesterified in the usual manner with a suitable carboxyl-protecting groupand preferably with benzhydryl.

It should be appreciated by those skilled in the art that the alcoholVIIa may form the corresponding lactone XV in the dehydration reaction.The production of the lactone XV will depend on the relativestereochemical configuration of the hydroxyl and carboxyl radicals ofthe alcohol VIIa which are used in the dehydration reaction. ##STR13##The trans-olefin VIII, wherein R³ is a carboxyl-protecting group, maythen be prepared directly by the addition of an alcohol, for example,benzhydryl alcohol, to the dehydration reaction employing the lactoneXV.

In one specific example wherein R¹ and R², taken together, ismethylenedioxy, R⁴ and R⁶ are methoxy and R⁵ is methyl, the alcohol VIIbwas dehydrated and then esterified in the usual manner with benzhydrylalcohol to produce the trans-olefin VIIIa.

In another specific example, the lactone XVa was isolated from one ofthe dehydration reactions employing the corresponding alcohol VIIb.Treatment of the resulting lactone XVa with benzhydryl alcohol understandard acidic dehydration conditions produced the desired trans-olefinVIIIa as shown below. ##STR14##

In an alternate reaction route, when it is desired to retain the same R³carboxyl-protecting group, the selective reduction of the aryltetraloneVI may be carried out by catalytic hydrogenation employing hydrogenationcatalysts such as palladium, platinum, Raney nickel or ruthenium, beingoptionally supported on a conventional carrier such as carbon,diatomaceous earth, etc., in non-reducible inert solvents such asmethanol, ethanol or ethyl acetate. Hydrogenation is preferablyconducted at room temperature and at atmospheric or slightly elevatedpressure. More preferably, the aryltetralone VI is reduced in a suitablesolvent with a selective reducing agent, e.g., sodium borohydride,sodium cyanoborohydride, zinc borohydride, sulfurated sodium borohydride(NaBH₂ S₃), disiamylborane, diborane, ammonium borane, t-butylamineborane, pyridine borane, lithium tri-s-butylborohydride, or othersimilar reducing agents which will not reduce the carboxylic esterradical. The alcohol VII which is produced is then subjected to standarddehydration conditions with a small amount of organic or mineral acidsuch as p-toluenesulfonic acid or sulfuric acid to produce thetrans-olefin VIII, wherein R³ is a carboxyl-protecting group. Thereaction is carried out in a suitable inert organic solvent, e.g.toluene, benzene, ether or methylene chloride, in the presence of adrying agent, e.g. Na₂ SO₄, MgSO₄, molecular sieves, etc., orpreferably, the water which is produced is azeotropically removed with aDean-Stark trap or similar apparatus.

Conversion of the trans-olefin VIII to the cis-olefin IX may be effectedby the epimerization of the carboxylic ester radical. This epimerizationis usually carried out in an inert organic solvent such as THF and atlow temperatures from about -78° C. to -20° C. and preferably at about-78° C. while employing a strong base such as lithium hydride, potassiumbis(trimethylsilyl)amide, lithium diisopropylamide or lithiumbis(trimethylsilyl)amide. The resulting anion is then quenched withacid, for example, mineral acids such as hydrochloric acid, sulfuricacid or the like, to produce stereoselectively the cis-olefin IX.

In another aspect of the present invention, there are provided compoundsof the formula ##STR15## wherein R¹ and R² each are independentlyhydrogen or (lower)alkoxy, or R¹ and R², taken together, ismethylenedioxy; R³ is hydrogen or a carboxyl-protecting group; R⁴ and R⁶each are independently hydrogen or (lower)alkoxy; and R⁵ is hydrogen ora phenol-protecting group; or an acid addition salt thereof.

In a preferred embodiment, there are provided compounds of the formula##STR16## wherein R³ is hydrogen or a carboxyl-protecting group, and R⁵is hydrogen or a phenol-protecting group; or an acid addition saltthereof.

In a more preferred embodiment, there are provided compounds of theFormula XVIa wherein R³ is (lower)alkyl or diphenylmethyl and R⁵ ismethyl or benzyl.

The cis-aryltetralone of Formula XVI may be prepared by theepimerization of the corresponding trans-aryltetralones VI. Compounds ofFormula XVI are then reduced and dehydrated to produce cis-olefins ofFormula XI according to Reaction Scheme 4. ##STR17##

The starting aryltetralone VI, with the ester radical in the relativetrans configuration, is epimerized to the cis-aryltetralone XVI at lowtemperatures from about -70° C. to -20° C. and preferably at about -78°C. by enol quenching utilizing a strong base such as lithium hydride,potassium bis(trimethylsilyl)amide, lithium diisopropylamide or lithiumbis(trimethylsilyl)amide in an inert organic solvent such as THF andthen adding a mineral acid, for example, hydrochloric acid.

The resulting cis-aryltetralone XVI may then be subjected to selectivereducing conditions to effect the reduction of the ketone radical to thealcohol XVII wherein R³ is a carboxyl-protecting group. The reductionmay be carried out by catalytic hydrogenation employing hydrogenationcatalysts such as palladium, platinum, Raney nickel or ruthenium, beingoptionally supported on a conventional carrier such as carbon,diatomaceous earth, etc., in non-reducible inert solvents such as water,methanol, ethanol or ethyl acetate. Hydrogenation is preferablyconducted at room temperature and at atmospheric or slightly elevatedpressure. More preferably, the aryltetralone XVI is reduced in asuitable solvent with a selective reducing agent, e.g. sodiumborohydride, sodium cyanoborohydride, zinc borohydride, sulfuratedsodium borohydride (NaBH₂ S₃), disiamylborane, diborane, ammonia borane,t-butylamine borane, pyridine borane, lithium tri-s-butylborohydride, orother similar reducing agents which will not reduce, hydrolyze norepimerize the carboxylic ester radical. The alcohol XVII which isproduced may then be subjected to standard dehydration conditions with asmall amount of organic or mineral acid such as p-toluenesulfonic acidor sulfuric acid to produce the cis-olefin IX, wherein R³ is acarboxyl-protecting group. The reaction is carried out in a suitableinert organic solvent, e.g., toluene, benzene, ether or methylenechloride, in the presence of a drying agent, e.g. Na₂ SO₄, MgSO₄,molecular sieves, etc., or preferably, the water which is produced isazeotropically removed with a Dean-Stark trap or similar apparatus.

According to another reaction route, the cis-aryltetralone XVI isreduced in a suitable solvent with a selective reducing agent,preferably lithium borohydride, to give the alcohol XIIa and/or thelactone having the formula XVIII. ##STR18##

It should be appreciated by those skilled in the art that the alcoholXIIa may form the corresponding lactone XVIII in the reduction andworkup. The amount of lactone XVIII isolated from the reaction willdepend on the relative stereochemical configuration of the hydroxyl andcarboxyl radicals of the alcohol XIIa which was produced in thereduction. In the specific example wherein R¹ and R², taken together, ismethylenedioxy, R⁴ and R⁶ are methoxy and R⁵ is methyl, the lactoneXVIIIa was the preferred product isolated from the reaction mixture.##STR19##

The resulting lactone XVIIIa may then be treated with an alcohol, andpreferably with benzhydryl alcohol, under standard acidic dehydrationconditions, as described above for lactone XVa, to produce the desiredcis-olefin IX wherein R³ is a carboxyl-protecting group.

According to another aspect of the present invention, there are providedcompounds of the formula ##STR20## wherein R¹ and R² each areindependently hydrogen or (lower)alkoxy, or R¹ and R², taken together,is methylenedioxy; R³ is hydrogen or a carboxyl-protecting group; R⁴ andR⁶ each are independently hydrogen or (lower)alkoxy; R⁵ is hydrogen or aphenol-protecting group; and R⁷ is hydrogen, halogen,(lower)alkoxycarbonyl, carboxyl, cyano, trimethylsilyl, phenylsulfonylor phenoxycarbonyl in which the phenyl ring of R⁷ may contain one or twosubstituents independently selected from (lower)alkyl, halogen,(lower)alkoxy and trifluoromethyl.

In a preferred embodiment, there are provided compounds of the formula##STR21## wherein R³ is hydrogen or a carboxyl-protecting group; R⁵ ishydrogen or a phenol-protecting group; and R⁷ is hydrogen, halogen,(lower)alkoxycarbonyl, carboxyl, cyano, trimethylsilyl, phenylsulfonylor phenoxycarbonyl in which the phenyl ring of R⁷ may contain one or twosubstituents independently selected from (lower)alkyl, halogen,(lower)alkoxy and trifluoromethyl.

In a more preferred embodiment, there are provided compounds of theFormula Xa wherein R³ is hydrogen, (lower)alkyl or diphenylmethyl; R⁵ ismethyl or benzyl; and R⁷ is bromine or chlorine.

The compounds of Formula X may be prepared from the correspondingcis-olefins of the Formula IX by employing a [3+2] cycloadditionreaction as shown in Scheme 5. ##STR22##

The cis-olefin IX is reacted with at least one equivalent of asubstituted nitrile oxide of the formula XX at about -20° C. torefluxing temperatures in an inert solvent (aqueous or organic, or mixedaqueous-organic) such as water, C₁ -C₆ alcohols, ethyl acetate, dioxane,tetrahydrofuran, acetone, nitromethane, methylene chloride or chloroformto give the isoxazole adduct X. Although the solvent and temperature ofthe reaction are not critical, it is preferred, when R⁷ is halogen, thatthe reaction be conducted near the refluxing temperature of the solvent,for example, acetone or ethyl acetate.

It is preferred to use an excess amount of the nitrile oxide XX in theabove 1,3-dipolar cycloaddition reaction, and more preferably, an excessof 3 equivalents is used. It is also preferred to generate the nitrileoxide XX in situ from the corresponding formaldoxime XIX in the presenceof an inorganic base such as KHCO₃ or Na₂ CO₃ or a trisubstituted aminesuch as triethylamine or pyridine as shown below: ##STR23## For thepreparation of Compound XXa, wherein R⁷ is bromo, the bromonitrile oxideis generated from dibromoformaldoxime XIX wherein R⁷ is bromine asdescribed in Tetrahedron Letters 21, 229-230 (1980), or more preferablyby the modified procedure described herein in Example 20, Step A.Another nitrile oxides of the formula XX wherein R⁷ is hydrogen;ethoxycarbonyl, carboxyl and cyano; trimethylsilyl; and phenylsulfonylmay be prepared by the general procedures described in TetrahedronLetters, 24, 1815-1816 (1983); J. Org. Chem., 48, 366-372 (1983);Synthesis, 719 (1982); and J. Org. Chem., 48, 1796-1800 (1983),respectively, and references therein.

In the specific example with Compound X, wherein R¹ and R², takentogether, is methylenedioxy; R⁴ and R⁶ are methoxy; R⁵ is methyl; R⁷ isbromine; and R³ is diphenylmethyl, deblocking of the carboxyl-protectinggroup with dry HCl in an inert organic solvent such as nitromethanereadily gave crystaline isoxazole acid Xc, wherein R³ is hydrogen and R⁷is chlorine. This particular deblocking procedure of a compound ofFormula X resulted in halogen displacement wherein the bromine radicalof R⁷ in the isoxazole ring was replaced by chlorine. When it is desiredto retain the bromine radical of R⁷, then the deblocking procedure ispreferably carried out with trifluoroacetic acid as is demonstratedherein for the preparation of the isoxazole acid Xd.

The stereospecific construction of the isoxazole ring in Compound Xwhich was produced by the approach of the substituted nitrile oxide XXwith diastereoface selection to the β face of the cis-olefin IX, can bereadily determined by ¹ H NMR spectroscopy. However, in order to provideadditional evidence of the regiospecific and stereospecific nature ofthe present invention, the [3+2] cycloaddition reaction was repeatedwith the trans-olefin VIIIb as shown below: ##STR24##

The isolation of Compound XXI containing the opposite stereochemistry inthe attachment of the isoxazole ring confirms that the process of theinvention described herein for the preparation of Compound X is a highlystereoselective process for producing the desired regiospecificityrequired for the efficient synthesis of epipodophyllotoxin andepipodophyllotoxin-related derivatives.

According to a further aspect of the present invention, there areprovided compounds of the formula ##STR25## wherein R¹ and R² each areindependently hydrogen or (lower)alkoxy, or R¹ and R², taken together,is methylenedioxy; R³ is hydrogen or a carboxyl-protecting group; R⁴ andR⁶ each are independently hydrogen or (lower)alkoxy; R⁵ is hydrogen or aphenol-protecting group; and R⁸ is cyano, aminomethyl, formyl orcarbamoyl; or an addition salt thereof.

In a preferred emodiment, there are provided compounds of the formula##STR26## wherein R³ is hydrogen or a carboxyl-protecting group; and R⁵is hydrogen or a phenol-protecting group; or an acid addition saltthereof.

In a more preferred embodiment, there are provided compounds of theFormula XIa wherein R³ is hydrogen, (lower)alkyl or diphenylmethyl andR⁵ is methyl or benzyl; or an acid addition salt thereof.

In another preferred embodiment, there are provided compounds of theformula ##STR27## wherein R³ is hydrogen or a carboxyl-protecting group;and R⁵ is hydrogen or a phenol-protecting group; or an addition saltthereof.

In a more preferred embodiment, there are provided compounds of theFormula XIb wherein R³ is hydrogen, (lower)alkyl or diphenylmethyl andR⁵ is methyl or benzyl; or an addition salt thereof.

The epipodophyllotoxin and epipodophyllotoxin related derivatives ofFormula XII may be prepared from the corresponding isoxazole compoundsof Formula X by the sequence described in Scheme 6. ##STR28##

Compounds of the Formula X are subjected to reaction conditions toprovide N--O bond heterolysis. The conditions for cleaving the isoxazolering will normally vary depending on the R⁷ substituted and whether R³is hydrogen or a carboxyl-protecting group. For example, when R⁷ istrimethylsilyl, thermal rearrangement followed by hydrolysis accordingto the general procedures described in Heterocycles, 20, 511-518 (1983)will produce compounds of the Formula XIc. When R⁷ is alkoxycarbonyl,phenylcarbonyl or cyano, hydrolysis to compound X wherein R⁷ is carboxylfollowed by decarboxylation according to the general proceduresdescribed in J. Org. Chem., 48, 366-372 (1983) will also providecompounds of the Formula XIc. In the case where R⁷ is phenylsulfonyl andR³ is hydrogen or a carboxyl-protecting group, selective reduction with,for example, sodium borohydride or 2% sodium amalgam according to thegeneral procedures described in J. Org. Chem., 49, 123-125 (1984) and J.Am. Chem. Soc., 101, 1319 (1979) will produce compounds of the FormulaXIc. Additionally, if a stronger reducing agent such as lithium aluminumhydride is employed with a compound of Formula X wherein R³ is hydrogen,then the resulting cyano compound of Formula XIc may, without isolation,be further reduced to produce the aminomethyl compound of Formula XId.Furthermore, it has been found that the isoxazole of Formula X whereinR⁷ is bromo may be reduced to Compound XIc with tributyltin hydride inthe presence of a free radical initiator such as2,2'-azobisisobutyronitrile. More preferably, reduction of Compounds Xwherein R⁷ is chlorine or bromine is carried out by catalytichydrogenation. The reduction is preferably conducted at initialpressures of about 40-50 psig of hydrogen in the presence of a catalystsuch as Raney nickel, platinum oxide, palladium on carbon or nickelboride in a non-reducing solvent, e.g. alcohols, ethyl acetate, water orthe like, or mixtures thereof. When the reduction is carried out with acompound of Formula X wherein R³ is other than hydrogen, then the pH ofthe solution may be adjusted to prevent the possible epimerization ofthe carboxyl group by adding a suitable buffering agent such as boricacid or other similar mild buffering acid. If Compound X wherein R³ ishydrogen is used, then the reaction is less sensitive to the reactionconditions and the buffering agent may be omitted.

Compounds of the Formula XIc wherein R³ is hydrogen or acarboxyl-protecting group are then selectively reduced to effect thereduction of the cyano radical to the aminomethyl compounds of theFormula XId. When R³ is a carboxyl-protecting group, the reduction maybe carried out by catalytic hydrogenation employing hydrogenationcatalysts such as platinum oxide or Raney nickel in non-reducible inertsolvents such as water, methanol, ethanol or ethyl acetate, or mixturesthereof. Hydrogenation is preferably conducted at room temperature andat atmospheric or slightly elevated pressure. Alternatively, thereduction may be carried out with selective reducing agents such asdiborane in tetrahydrofuran or other similar reducing agents which willnot reduce nor epimerize the carboxylic ester radical. The resultingcompounds of Formula XId wherein R³ is a carboxyl-protecting group maythen be removed under non-epimerizing conditions, e.g. hydrogenolysis oracid hydrolysis.

More preferably, the reduction of the cyano radical of Compounds XIcwherein R³ is hydrogen is carried out by catalytic hydrogenationemploying hydrogenation catalysts such as platinum oxide or Raney nickelin non-reducible inert solvents such as methanol, ethanol, ethylacetate, methylene chloride or mixtures thereof. Hydrogenation ispreferably conducted at room temperature and at atmospheric or slightlyelevated pressure. Most preferably, the reduction is carried out withlithium aluminum hydride in a suitable solvent such as tetrahydrofuran.The resulting product of Formula XId wherein R³ is hydrogen may, ifdesired, be isolated in the form of an addition salt such as an aceticacid salt.

The aminomethyl compounds of Formula XId wherein R³ is hydrogen are thencyclized by diazotization of the primary amine, and preferably withsodium nitrite or i-amyl nitrite in an aqueous acidic medium such asaqueous acetic acid or aqueous trifluoroacetic acid. The cyclizationproceeds directly to the desired lactones of the Formula XII having thecorrect relative stereochemistry of epipodophyllotoxin andpodophyllotoxin.

Compounds of the Formula XIc may, if desired, be selectively convertedto compounds of the Formula XI wherein R⁸ is formyl by methodswell-known to those skilled in the art such as catalytic hydrogenationwith Raney nickel in the presence of sodium hypophosphite in aqueousacetic acid or zinc in acetic acid. The compounds of Formula XI whereinR⁸ is formyl and R³ is hydrogen may then be selectively reduced to thealcohol epipodophyllic acid which may be converted to epipodophyllotoxinand related compounds by the method described in J. Am. Chem. Soc., 103,6208-6209 (1981).

Compounds of the Formula XIc may, if desired, be selectively convertedto compounds of the Formula XI wherein R⁸ is carbamoyl with e.g.,hydrogen peroxide. The compounds of Formula XI wherein R⁸ is carbamoyland R³ is hydrogen may then be selectively reduced with e.g., lithiumaluminum hydride, to provide compounds of the Formula XId wherein R³ ishydrogen, which are converted to epipodophyllotoxin and relatedcompounds by the methods described herein.

In a more preferred reaction pathway, the compounds of Formula XIb neednot be isolated and may be reacted further to the desiredepipodophyllotoxin (I) and related compounds. Thus, for example, thecompound of Formula XIa wherein R⁵ is methyl and R³ is hydrogen is firsttreated with a reducing agent such as lithium aluminum hydride to effectreduction of the cyano radical. After the evaporation of the solvent,the resulting crude product of Formula XIb is then treated with asolution of sodium nitrite to effect diazotization and subsequentlactonization to produce the desired epipodophyllotoxin (I), as shownbelow: ##STR29##

In a still more preferred reaction pathway, the compounds of FormulaeXIa and XIb need not be isolated and may be treated further to thedesired epipodophyllotoxin (I). Thus, for example, the compound ofFormula Xa wherein R⁵ is methyl, R³ is hydrogen and R⁷ is chlorine issequentially treated with nickel boride and then platinum oxide at roomtemperature under an initial hydrogen pressure of about 40-50 psi. Theresulting crude product of Formula XIb, without further isolation andpurification, is treated with diazotizing agent and preferably withsodium nitrite in an acid medium such as aqueous acetic acid to give thedesired epipodophyllotoxin (I).

In still another aspect of the present invention, there are providedcompounds of the formula ##STR30## wherein R¹ and R² each areindependently hydrogen or (lower)alkoxy, or R¹ and R², taken together,is methylenedioxy; R³ is hydrogen or a carboxyl-protecting group; R⁴ andR⁶ each are independently hydrogen or (lower)alkoxy; R⁵ is hydrogen or aphenol-protecting group; and R⁹ is phenyl or (lower)alkyl optionallysubstituted by one or more halogen atoms selected from fluorine,chlorine and bromine.

In a preferred embodiment, there are provided compounds of the formula##STR31## wherein R³ is hydrogen or a carboxyl-protecting group; R⁵ ishydrogen or a phenol-protecting group; and R⁹ is phenyl or (lower)alkyloptionally substituted by one or more halogen atoms selected fromfluorine, chlorine and bromine.

In a still more preferred embodiment, there are provided compounds ofthe Formula XIVa wherein R³ is diphenylmethyl; R⁵ is methyl or benzyl;and R⁹ is methyl.

The compounds of Formula XIV may be prepared from the correspondingcompounds of the Formula XIII by an efficient and improved cyclizationprocedure. The cyclopropane compounds XIII are themselves prepared fromthe readily available chalcones XXII. The synthetic sequence for thepreparation of compounds XIV as well as their use in the preparation ofthe aryltetralones VI is outlined in Scheme 7. ##STR32##

The starting materials of the Formula XXII are readily prepared fromknown ketones and aryl aldehydes by the general procedures described byS. Wattanasin and W. S. Murphy in Synthesis, 647-650 (1980).

The cyclopropanation of the chalcones of Formula XXII to give thecyclopropyl ketones XIII may advantageously be carried out withwell-known cyclopropanating agents, e.g. ethoxycarbonyldimethylsulphonium methylide by the general procedure described by W. S.Murphy and S. Wattanasin in J. C. S. Perkin I, 271-276 (1982). Themethod of Murphy and Wattanasin, however, results in the formation ofabout a 1:1 mixture of α--COOR³ and β--COOR³ epimers of compounds ofFormula XIII. It was also suggested by Murphy et al. that the α-isomeris the more important isomer for the subsequent cyclization reactionsince the β-isomer epimerizes to the α-isomer under Lewis acidconditions within 10 minutes.

We have now found that the α--COOR³ isomer of the cyclopropyl ketoneXIIIa is formed exclusively in 96% yield when the cyclopropanationreaction is conducted in dimethylsulfoxide with the correspondingchalcone XXIIa wherein R¹ and R², taken together, is methylenedioxy; R⁴and R⁶ is methoxy; R⁵ is methyl and R³ is ethyl.

The direct conversion by Lewis acid-catalyzed reactions of some of thecyclopropyl ketones of Formula XIII to the transaryltetralones ofFormula VI is well-documented by W. S. Murphy and S. Wattanasin in J. C.S. Perkin I, 271-276 (1982) and references therein. Murphy et al.describe the successful cyclization of compound XIIIa wherein R¹ and R²,taken together, is methylenedioxy; R⁴ and R⁶ are methoxy; R⁵ is methyland R³ is ethyl to the corresponding important Gensler ketone VIb. Thecyclization is characterized by the dramatic effect of the use ofnitromethane as the solvent and the unsuccessful attempts to achive thisrearrangement in benzene and methylene chloride under a variety ofconditions [W. S. Murphy and S. Wattanasin, J. C. S. Chem. Comm.,262-263 (1980)]. However, the rearrangement of compound XIIIa to thearyltetralone VIb by the method of Murphy et al. proceeded rather slowlyand yielded mixture of products. The best procedure utilizing BF₃.Et₂ Oin nitromethane for 15 days afforded a mixture of products and, at most,produced a 57% yield of compound VIb after preparative thin-layerchromatography as illustrated in Scheme 8. ##STR33##

It is the purpose of the present embodiment of the invention to describea new and significant improvement in the preparation of thearyltetralones VI via the novel enol compounds XIV.

A compound of Formula XIII is treated at about room temperature with anamount of about 0.5 equivalent of a Lewis acid, for example, SnCl₄,BF₃.Et₂ O, ZnCl₂ or the like and at least 1 equivalent of an acidanhydride, for example, acetic anhydride or trifluoroacetic anhydride inan inert organic solvent such as nitromethane, methylene chloride,benzene, tetrahydrofuran, ethyl acetate, toluene, chloroform, dioxane,etc., to produce the enol compound of the Formula XIV. The solvent to beemployed in the present embodiment is not critical. It is preferred toutilize 1 equivalent of a Lewis acid and 1 equivalent or, morepreferably, 2 equivalents of an acid anhydride of the formula ##STR34##wherein R⁹ is as defined above. When the Lewis acid BF₃.Et₂ O isutilized, it is advantageous to terminate and work up the reaction inabout 5 minutes. However, if a weaker Lewis acid such as ZnCl₂ isutilized in the reaction, then it is preferred to continue the reactionfor 24 hours before isolation of the corresponding enol compound XIV.

When it is desired to produce the aryltetralones VI, the cyclization ofthe corresponding cyclopropylketones XIII is carried out under the sameconditions as described above for the preparation of the enol compoundsXIV except that the reaction is allowed to proceed until the conversionto the aryltetralones VI is complete. Additionally, it was found thatthe cyclization reaction may be conducted with a catalytic amount ofabout 0.1 equivalent of an acid anhydride. It is preferred that thecyclization be carried out with 1 equivalent of an acid anhydride andmost preferably with 2 equivalents in order to complete the reaction inabout 1 to 2 hours and provide a purer product. In a procedure utilizinga weak Lewis acid such as ZnCl₂ and 2 equivalents of acid anhydride, itis preferred that the reaction be allowed to proceed for more than 24hours. It is understood that if less than about 1 to 2 equivalents of anacid anhydride is used in the cyclization reaction, then longer reactiontimes may be necessary to complete the reaction.

In one of the specific examples exemplified in the present invention andillustrated in Scheme 9, ##STR35## compound XIIIa was treated with 1equivalent of BF₃.Et₂ O and 2 equivalents of acetic anhydride toproduce, in about 1 hour via the enol intermediate XIVb, a 96% yield ofthe aryltetralone VIb. In another example, Compound XIIIa was treatedwith 1 equivalent of ZnCl₂ and 2 equivalents of acetic anhydride toproduce, in about 24 hours, a greater than 90% yield of the enolcompound XIVb. The above examples, as well as other examples utilizingan acid anhydride, clearly and dramatically illustrate the generalapplicability and advantages of the present invention.

According to the present invention, there is also provided a process forpreparing a compound of the formula ##STR36## wherein R¹ and R² each areindependently hydrogen or (lower)alkoxy, or R¹ and R², taken together,is methylenedioxy; R⁴ and R⁶ each are independently hydrogen or(lower)alkoxy; and R⁵ is hydrogen or a phenol-protecting group, or apharmaceutically acceptable addition salt thereof, comprising the stepsof:

(a) reacting a cis-olefin of the formula ##STR37## wherein R³ ishydrogen or a carboxyl-protecting group; and R¹, R², R⁴, R⁵ and R⁶ areas defined above, with a nitrile oxide of the formula ##STR38## whereinR⁷ is hydrogen, halogen, (lower)alkoxycarbonyl, carboxyl, cyano,trimethylsilyl, phenylsulfonyl or phenoxycarbonyl in which the phenylring of R⁷ may contain one or two substituents independently selectedfrom (lower)alkyl, halogen, (lower)alkoxy and trifluoromethyl, in aninert solvent, to produce an isoxazole of the formula ##STR39## whereinR¹, R², R³, R⁴, R⁵, R⁶ and R⁷ are as defined above;

(b) cleaving the isoxazole ring of Formula X to produce a compound ofthe formula ##STR40## wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as definedabove;

(c) selectively reducing the nitrile of Formula XIc to produce acompound of the formula ##STR41## wherein R¹, R², R³, R⁴, R⁵ and R⁶ areas defined above, or a salt thereof; and, if R³ is a carboxyl-protectinggroup, removing said carboxyl-protecting group to produce a compound ofthe Formula XId wherein R³ is hydrogen; and

(d) cyclizing the compound of Formula XId by diazotization of the aminoradical followed by lactonization to produce a compound of the formula##STR42## wherein R¹, R², R⁴, R⁵ and R⁶ are as defined above.

A preferred embodiment of the present invention is the process ofpreparing an epipodophyllotoxin compound of the formula ##STR43##wherein R⁵ is hydrogen or a phenol-protecting group, comprising thesteps of:

(a) reacting a cis-olefin of the formula ##STR44## wherein R³ ishydrogen or a carboxyl-protecting group and R⁵ is hydrogen or aphenol-protecting group, with a nitrile oxide of the formula ##STR45##wherein R⁷ is hydrogen, halogen, (lower)alkoxycarbonyl, carboxyl, cyano,trimethylsilyl, phenylsulfonyl or phenoxycarbonyl in which the phenylring of R⁷ may contain one or two substituents independently selectedfrom (lower)alkyl, halogen, (lower)alkoxy and trifluoromethyl, in aninert solvent, to produce an isoxazole of the formula ##STR46## whereinR³, R⁵ and R⁷ are as defined above; (b) cleaving the isoxazole ring ofFormula Xa to produce a compound of the formula ##STR47## wherein R³ andR⁵ are as defined above; (c) selectively reducing the nitrile of FormulaXIa to produce a compound of the formula ##STR48## wherein R³ and R⁵ areas defined above or a salt thereof; and, if R³ is a carboxyl-protectinggroup, removing said carboxyl-protecting group to produce a compound ofthe Formual XIb wherein R³ is hydrogen; and

(d) cyclizing the compound of Formula XIb by diazotization of the aminoradical followed by lactonization to produce an epipodophyllotoxincompound of the formula ##STR49## wherein R⁵ is as defined above.

Another embodiment of the present invention is the process for preparinga cis-olefin of the formula ##STR50## wherein R¹ and R² each areindependently hydrogen or (lower)alkoxy, or R¹ and R², taken together,is methylenedioxy; R³ is hydrogen or a carboxyl-protecting group; R⁴ andR⁶ each are independently hydrogen or (lower)alkoxy; and R⁵ is hydrogenor a phenol-protecting group, comprising the steps of:

(a) dehydrating an alcohol of the formula ##STR51## wherein R³ is acarboxyl-protecting group; R⁵ is a phenol-protecting group; and R¹, R²,R⁴ and R⁶ are as defined above, in the presence of an acid to produce atrans-olefin of the formula ##STR52## wherein R¹, R², R³, R⁴, R⁵ and R⁶are defined above; and

(b) epimerizing the trans-olefin of the Formula VIII by treatment with astrong base at low temperatures in an inert organic solvent followed byquenching with acid to produce a cis-olefin of the formula ##STR53##wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as defined above, and optionallyand selectively deblocking to produce a compound of Formula IX whereinR³ is hydrogen and R⁵ is a phenol-protecting group or R⁵ is hydrogen andR³ is a carboxyl-protecting group.

Another preferred embodiment of the present invention is thestereospecific process of preparing an isoxazole compound of the formula##STR54## wherein R³ is hydrogen or a carboxyl-protecting group; R⁵ ishydrogen or a phenol-protecting group and R⁷ is hydrogen, halogen,(lower)alkoxycarbonyl, carboxyl, cyano, trimethylsilyl, phenylsulfonylor phenoxycarbonyl in which the phenyl ring of R⁷ may contain one or twosubstituents independently selected from (lower)alkyl, halogen,(lower)alkoxy and trifluoromethyl, comprising the step of reacting acis-olefin of the formula ##STR55## wherein R³ and R⁵ are as definedabove with a nitrile oxide of the formula ##STR56## wherein R⁷ is asdefined above in an inert aqueous or organic, or mixed aqueous-organicsolvent at about -20° C. to refluxing temperature of the solvent tostereoselectively produce said isoxazole compound of the Formula Xa andoptionally and selectively deblocking said compound of Formula Xawherein R³ is a carboxyl-protecting group to produce a compound of theformula ##STR57## wherein R⁵ and R⁷ are as defined above.

Still another preferred embodiment of the present invention is theprocess of preparing an epipodophyllotoxin compound of the formula##STR58## wherein R⁵ is hydrogen or a phenol-protecting group,comprising the steps of:

(a) cleaving the isoxazole ring of the formula ##STR59##

wherein R⁵ is hydrogen or a phenol-protecting group and R⁷ is chlorineor bromine, to produce a nitrile of the formula ##STR60## wherein R⁵ ishydrogen or a phenol-protecting group; (b) selectively reducing thenitrile of Formula XIe to produce a compound of the formula ##STR61##wherein R⁵ is hydrogen or a phenol-protecting group; and (c) cyclizingthe compound of Formula XIf by diazotization of the amino radicalfollowed by lactonization to produce an epipodophyllotoxin compound ofthe formula ##STR62## wherein R⁵ is hydrogen or a phenol-protectinggroup.

A variation of the above-described process for preparing compounds ofthe Formula XII involves the selective reduction of thetrans-aryltetralone of Formula VI under hydrolyzing conditions orhydrolysis of the carboxylic ester of the trans-aryltetralone of FormulaVI followed by selective reduction of the resultant acid VIa to producea compound of Formula VIIa. Compound VIIa is then treated underdehydrating conditions in the presence of an acid to produce atrans-lactone of the formula ##STR63## wherein R¹, R², R⁴, R⁵ and R⁶ areas defined above. Compound XV is dehydrated in the presence of an acidand an alcohol R³ OH to produce a trans-olefin of the Formula VIIIwherein R³ is a carboxyl-protecting group. The trans-olefin VIII is thenepimerized by enolate quenching to produce a cis-olefin of Formula IX.Compound IX is then reacted with a nitrile oxide of the Formula XX andthe isoxazole of Formula X which is thereby produced is sequentiallycleaved to a nitrile of Formula XIa and reduced to an amine of formulaXIb, and then diazotized according to the process described above toproduce the desired compound of Formula XII.

A further variation of the above-described process for preparing theepipodophyllotoxin and epipodophyllotoxin related compounds of FormulaXII involves epimerizing the trans-aryltetralone of Formula VI byenolate quenching to produce a cis-aryltetralone of the formula##STR64## wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as defined above.Compound XVI is then selectively reduced to produce a compound of theformula ##STR65## wherein R¹, R², R³, R⁴, R⁵ and R⁶ are defined above.Compound XVII is then dehydrated in the presence of an acid with removalof the water which is formed to produce a cis-olefin of the formula##STR66## wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as defined above. Thecis-olefin of the Formula IX is then reacted with a nitrile oxide of theFormula XX, and the isoxazole of Formula X which is thereby produced issequentially cleaved to a nitrile of the Formula XIa and reduced to anamine of the Formula XIb, and then diazotization according to theprocess described above to produce the desired compound of Formula XII.

A still further variation of the above-described process for preparingcompounds of the Formula XII involves epimerizing thetrans-aryltetralone of Formula VI by enolate quenching to produce acis-aryltetralone of the formula ##STR67## wherein R¹, R², R³, R⁴, R⁵and R⁶ are as defined above. Compound XVI is then selectively reducedunder hydrolyzing conditions or hydrolyzed followed by selectivereduction to produce a compound of the formula ##STR68## wherein R¹, R²,R⁴, R⁵ and R⁶ are as defined above. Compound XVIII is dehydrated in thepresence of an acid and an alcohol R³ OH to produce a cis-olefin of theformula ##STR69## wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as definedabove. The cis-olefin of Formula IX is then reacted with a nitrile oxideof the Formula XX, and the isoxazole of the Formula X which is therebyproduced is sequentially cleaved to a nitrile of the Formula XIa andreduced to an amine of the Formula XIb, and then diazotization accordingto the process described above to produce the desired compound ofFormula XII.

In another aspect of the present invention, there is provided a processfor preparing a compound of the formula ##STR70## wherein R¹ and R² eachare independently hydrogen or (lower)alkoxy, or R¹ and R², takentogether, is methylenedioxy; R³ is hydrogen or a carboxyl-protectinggroup; R⁴ and R⁶ each are independently hydrogen or (lower)alkoxy; andR⁵ is hydrogen or a phenol-protecting group, comprising the step ofcyclizing a cyclopropyl compound of the formula ##STR71## wherein R¹,R², R³, R⁴, R⁵ and R⁶ are as defined above by treatment with at least0.5 equivalent of a Lewis acid and at least one equivalent of an acidanhydride of the formula ##STR72## wherein R⁹ is phenyl or (lower)alkyloptionally substituted by one or more halogen atoms selected fromfluorine, chlorine and bromine in an inert solvent until substantiallythe compound of the formula ##STR73## is produced wherein R¹, R², R³,R⁴, R⁵, R⁶ and R⁹ are as defined above.

In still another aspect of the present invention, there is provided aprocess for preparing a compound of the formula ##STR74## wherein R¹ andR² each are independently hydrogen or (lower)alkoxy, or R¹ and R², takentogether, is methylenedioxy; R³ is hydrogen or a carboxyl-protectinggroup; R⁴ and R⁶ each are independently hydrogen or (lower)alkoxy; andR⁵ is hydrogen or a phenol-protecting group, comprising the step ofcyclizing a cyclopropyl compound of the formula ##STR75## wherein R¹,R², R³, R⁴, R⁵ and R⁶ are as defined above by treatment with at least0.5 equivalent of a Lewis acid and at least a catalytic amount of anacid anhydride of the formula ##STR76## wherein R⁹ is phenyl or(lower)alkyl optionally substituted by one or more halogen atomsselected from fluorine, chlorine and bromine in an inert organic solventuntil substantially the trans-aryltetralone of the formula ##STR77## isproduced wherein R¹, R², R³, R⁴, R⁵ and R⁶ are as defined above.

A preferred embodiment of the present invention is the process ofpreparing a trans-aryltetralone of the formula ##STR78## wherein R³ ishydrogen or a carboxyl-protecting group and R⁵ is hydrogen or aphenol-protecting group, comprising the step of cyclizing a cyclopropylcompound of the formula ##STR79## wherein R³ is a carboxyl-protectinggroup and R⁵ is phenol-protecting group by treatment with about oneequivalent of a Lewis acid and about one to two equivalents of an acidanhydride of the formula ##STR80## wherein R⁹ is (lower)alkyl optionallysubstituted by one or more halogen atoms selected from fluorine,chlorine and bromine in an inert organic solvent until substantially thetrans-aryltetralone of formula ##STR81## is produced wherein R³ and R⁵are as defined above, and optionally and selectively deblocking toproduce a compound of Formula VIc wherein R³ is hydrogen and R⁵ is aphenol-protecting group or R⁵ is hydrogen and R³ is acarboxyl-protecting group.

DESCRIPTION OF SPECIFIC EMBODIMENTS

In the following examples, all temperatures are given in degreesCentigrade. Melting points were recorded on a Thomas-Hoover capillarymelting point apparatus and are uncorrected. ¹ H NMR spectra wererecorded on a Bruker WM 360 spectrometer in CDCl₃. Chemical shifts arereported in δ units and coupling constants in Hertz. Splitting patternsare designated as follows: s, singlet; d, doublet; t, triplet; q,qaurtet; m, multiplet; bp, broad peak; and dd, doublet of doublet.Infrared spectra were determined on a Beckman Model 4240spectrophotometer and are reported in reciprocal centimeters. Thin-layerchromatography (TLC) was carried out on precoated silica gel plates(60F-254) using UV light and/or iodine vapors as visualizing agents.Flash chromatography was run with Woelm silica gel (32-63 μm) and theindicated solvents. All evaporations of solvents were performed underreduced pressure. As used herein, the term Skellysolve B is a petroleumsolvent fraction having a bp range of 60°-68° C. Consisting essentiallyof n-hexane, and the term "ether" is diethyl ether unless otherwiseindicated.

EXAMPLE 1 Ethyl2-(3,4-methylenedioxybenzoyl)-3-(3,4,5-trimethoxyphenyl)cyclopropanecarboxylate (XIIIa) ##STR82##

In a three-neck one-liter round-bottom flask, equipped with a magneticstirrer, dropping funnel, nitrogen inlet and a septum was placed sodiumhydride (8.2 g, 0.17 moles, 50% dispersion). The dispersion was washedwith petroleum ether (2×100 ml) and dried under nitrogen.Trimethylsulfoxonium iodide (37.7 g, 0.17 moles) was added, followed bya dropwise addition of dry dimethylsulfoxide (45 ml) via a syringe overa 30-minute period. The suspension was stirred at room temperature for1.5 hours, and then a solution of carbethoxymethyl dimethysulfoniumbromide (41.2 g, 0.18 moles) in dimethylsulfoxide (60 ml) was added overa 10-minute period, under continuous stirring. The milky whitesuspension was further stirred at room temperature for 1.5 hours. Asuspension of 3,4,5-trimethoxy-3',4'-methylenedioxy chalcone XXIIa (55.9g, 0.16 moles) [prepared according to the procedure described by S.Wattanasin and W. S. Murphy, Synthesis, 647 (1980)] in dimethylsulfoxide(185 ml) was added in a steady stream over a 5-minute period, and thenthe reaction mixture was stirred at room temperature for 17 hours. Thereaction mixture was poured into cold 0.1N HCl (700 ml), and theresulting gummy material was separated from the aqueous solution. Theaqueous solution was extracted with ether (2×500 ml). The combinedextract together with an additional amount of ether (500 ml) wasemployed to dissolve the gummy precipitate. The etheral solution wassequentially washed with aqueous NaHCO₃ solution (500 ml, 5%) and water,dried (Na₂ SO₄ and MgSO₄) and concentrated to yield the α-isomer of thetitle compound (68.0 g) as a light-yellow glass. The ¹ H NMR spectraldata of this material was identical to the α-isomer reported by W. S.Murphy and S. Wattanasin, J.C.S. Perkin I, 271 (1982).

In another experiment, the trimethylsulfoxonium iodide which wasutilized in the above procedure was omitted from the reaction to alsoafford, in high yield, the α-isomer of the title compound. Thus, to asolution of sodium hydride (0.67 g, 1.4 mM), 50% dispersion) in 10 ml ofdry dimethylsulfoxide was added carbethoxymethyl dimethylsulfoniumbromide (2.98 g, 1.2 mM) followed by an additional 19 ml ofdimethylsulfoxide. After approximately 75 minutes, a solution of thechalcone XXIIa (3.42 g, 1.0 mM) in 21 ml of tetrahydrofuran and 4 ml ofdimethylsulfoxide was slowly added over a 35-minute period. The reactionmixture was worked up as in the above procedure to give the α-isomer ofthe title compound in 96% yield.

EXAMPLE 2 Trans-ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIb) ##STR83##

To a solution of cyclopropylketone XIIIa (0.8 g, 1.8 mM) in methylenechloride (40 ml) was added BF₃.Et₂ O (0.24 ml, 19 mM) followed by aceticanhydride (0.36 ml, 3.8 mM). The solution was stirred at roomtemperature for 2.5 hours and then diluted with 0.2N sodium hydroxidesolution (50 ml) and methylene chloride (50 ml). The organic layer wasseparated, washed (H₂ O), dried (MgSO₄) and concentrated to an oilysolid (0.72 g). Recrystallization from absolute ethanol with charcoaltreatment afforded the title compound as a white crystalline solid (0.46g); m.p. 157°-159° C. The ¹ H NMR spectral data was in agreement withthat reported by W. S. Murphy and S. Wattanasin, J.C.S. Perkin I, 271(1981).

EXAMPLE 3 Trans-ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIb)

The procedure of Example 2 was repeated with 50 mg (0.12 mM) ofcyclopropylketone XIIIa except that the methylene chloride utilizedtherein was replaced with nitromethane, and there was thereby produced45 mg of the title compound; TLC [silica gel/ether:Skellysolve B (3:2)]gave R_(f) =0.26. The ¹ H NMR spectral data was identical to the productproduced in Example 2.

EXAMPLE 4 Trans-ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIb)

(a) The procedure of Example 2 was repeated in methylene chloride with50 mg (0.12 mM) of cyclopropylketone XIIIa except that the BF₃.Et₂ Outilized therein was replaced with SnCl₄, and there was thereby producedabout 90% yield of the title compound.

(b) The above procedure (a) was repeated except that the methylenechloride utilized therein was replaced with nitromethane, and there wasthereby produced about 90% yield of the title compound.

(c) The above procedure (a) was again repeated except that the methylenechloride utilized therein was replaced with benzene, and there wasthereby produced the title compound.

The TLC [silica/ether:Skellysolve B (3:2)] of each of the above threeproducts gave R_(f) =0.26, and the ¹ H NMR spectral data were identicalto the product produced in Example 2.

EXAMPLE 5 Trans-ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIb)

The procedure of Example 3 was repeated with 428 mg (1.0 mM) ofcyclopropylketone XIIIa and 204 mg (2.0 mM) of acetic anhydride in 5 mlof nitromethane, except that the 1 equivalent of BF₃.Et₂ 0 utilizedtherein was replaced with 0.5 equivalent of BF₃.Et₂ O (71 mg, 0.5 mM),and there was thereby produced the title compound. The ¹ H NMR spectraldata was identical to the product produced in Example 3.

EXAMPLE 6 Trans-ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIb)

To a solution of cyclopropylketone XIIIa (428 mg, 1.0 mM) in 5 ml ofnitromethane was added a catalytic amount of acetic anhydride (10.2 mg,0.1 mM) followed by BF₃.Et₂ O (142 mg, 1.0 mM). The reaction was stirredat room temperature and followed by high pressure liquid chromatography.After about 100 hours, the reaction mixture was treated with 10 ml of0.2N NaOH and diluted with 5 ml of methylene chloride. The organic phasewas separated, dried and evaporated under reduced pressure to give thetitle compound. The ¹ H NMR spectrum was identical to the productproduced in Example 2 except for the presence of some impurities.

EXAMPLE 7 Trans-ethyl1,2-dihydro-6,7-methylenedioxy-4-acetoxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(XIVb) ##STR84##

To a solution of cyclopropylketone XIIIa (1.40 g, 3.24 mM) in methylenechloride (50 ml) was added acetic anhydride (0.61 ml, 6.47 mM) followedby BF₃.Et₂ O (0.40 ml, 3.25 mM). The solution was stirred for 5 minutesand then treated with 0.5N sodium hydroxide solution (35 ml). Theorganic layer was separated, washed (H₂ O), dried (MgSO₄) andconcentrated to a syrup (1.53 g). Thin-layer chromatography [ethylacetate:methylene chloride (5:95)] revealed two major spots at R_(f)'s=0.47 and 0.27 R_(f) of starting material=0.36). Silica gel columnchromatography, using 3% ethyl acetate in methylene chloride as elutingsolvent, afforded the two compounds in analytical purity.

The faster component (0.52 g, R_(f) =0.47) was characterized as thetitle compound, m.p. 124°-129° C.

Anal. Calc'd for C₂₅ H₂₆ O₉ : C, 63.82; H, 5.57. Found: C, 63.52; H,5.74.

¹ H NMR (CDCl₃, δ): 1.18(t, 3H, 7.2 Hz), 2.31(s, 3H), 3.62(t, 1H, 5.5Hz), 3.81(s, 9H), 4.10(q, 2H), 4.49(d, 1H, 5.5 Hz), 5.55(d, 1H, 5.7 Hz),5.92(s, 2H), 6.52(s, 3H), 6.68(s, 1H).

The slower component (0.40 g, R_(f) =0.27) was identified as thetetralone VIb, which was identical to the compound obtained in Example2.

EXAMPLE 8 Trans-ethyl1,2-dihydro-6,7-methylenedioxy-4-acetoxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(XIVb)

The procedure of Example 7 was repeated except that the BF₃.Et₂ Outilized therein was replaced with ZnCl₂ and, after 24 hours at roomtemperature, the reaction gave >90% yield of the title compound; TLC[silica/ethyl acetate:methylene chloride (5:95)] gave R_(f) =0.47. The ¹H NMR spectral data was identical to the product produced in Example 7.

EXAMPLE 9 Cis-ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(XVIb) ##STR85##

To a solution of 1.7M n-BuLi in hexane (10.6 ml, 18.0 mM) intetrahydrofuran (10 ml) at -78° C. and under nitrogen was added slowlydiisopropylamine (2.52 ml, 18.0 mM). After stirring the solution for 20minutes, a solution of trans-tetralone VIb (1.93 g, 4.51 mM) intetrahydrofuran (40 ml) was added dropwise over a period of 30 minutesat -78° C. After the addition was complete, the orange mixture wasslowly warmed to -40° C. over a 1-hour period and further stirred for 30minutes. A solution of concentrated HCl (3.5 ml) in tetrahydrofuran (3.5ml) was then added in one portion to yield a pale yellow solution. Afterwarming to room temperature, the mixture was diluted with 50 ml of waterand extracted with ethyl acetate. The combined organic extract was dried(MgSO₄) and concentrated to give 2.1 g of product, which wascrystallized from 95% ethanol. Recrystallization from absolute ethanolwith slow cooling to room temperature yielded the title compound as acrystalline solid, m.p. 136.5°-137.5° C. ¹ H NMR (CDCl₃, δ): 1.24(t, 3H,8 Hz), 2.88 (m, 2H), 3.52(m, 1H), 3.76(s, 6H), 3.84(s, 3H), 4.16(q, 2H,8 Hz), 4.72(d, 1H, 6 Hz), 6.10(s, 2H), 6.24(s, 2H), 6.68(s, 1H), 7.64(s,1H).

EXAMPLE 10 Ethyl1,2,3,4-tetrahydro-6,7-methylenedioxy-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIId) ##STR86##

To a solution of tetralone VIb (6.25 g, 14.6 mM) in 95% ethanol (100 ml)and methylene chloride (50 ml) was added a cold solution of sodiumborohydride (0.42 g, 11.1 mM) in water (5 ml). The solution was stirredat room temperature for 3 hours and at 40° C. for 30 minutes. Thesolution was diluted with water (50 ml) and concentrated to a solidresidue at 35° C. The residue was partitioned between methylene chloride(100 ml) and water (100 ml). The aqueous layer was further extractedwith methylene chloride (100 ml), and the combined organic extract wasdried (MgSO₄) and concentrated to a solid residue (5.95 g).Recrystallization from 95% ethanol afforded the title compound as acrystalline solid; m.p. 151°-152° C.

Anal. Calc'd for C₂₃ H₂₆ O₈ : C, 64.18; H, 6.09. Found: C, 64.03; H,6.02.

¹ H NMR (CDCl₃, δ): 1.15(t, 3H, 7.2 Hz), 2.06(m, 1H), 2.35(m, 1H),2.46(d, 1H, 8.6 Hz), 2.95(m, 1H), 3.78(s, 6H), 3.82(s, 3H), 4.06(q, 2H,7.2 Hz), 4.31(d, 1H, 7.7 Hz), 4.83(m, 1H), 5.91(2H), 6.24(s, 2H),7.07(s, 1H).

IR (KBr), νmax, cm⁻¹ : 3290, 1730, 1725, 1590, 1235, 1122.

EXAMPLE 11 Trans-ethyl1,2-dihydro-6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIIIb) ##STR87##

A suspension of alcohol VIId (0.43 g, 1.0 mM) in toluene (15 ml)containing p-toluenesulfonic acid monohydrate (4 mg) was heated toreflux with a Dean-Stark trap for 1 hour. Thin-layer chromatography[ethyl acetate:Skellysolve B (1:1)] revealed that all of the startingmaterial (R_(f) =0.40) was converted to a new compound (R_(f) =0.69).The solution was cooled, washed with 5% aqueous sodium bicarbonatesolution and water, followed by concentration under reduced pressure toan oil residue. The residue was purified by column chromatography oversilica gel (20 g) using methylene chloride and 3% ethyl acetate inmethylene chloride as eluting solvent to yield the title compound (R_(f)=0.69) as a white amorphous solid; m.p. 129.5°-130.5° C.

Anal. Calc'd for C₂₃ H₂₄ O₇ : C, 66.98; H, 5.87. Found: C, 66.83; H,5,87.

¹ H NMR (CDCl₃, δ): 1.14(t, 3H, 7.3 Hz), 3.58(m, 2H), 3.80(s, 6H),3.83(s, 3H), 4.07(q, 2H, 7.3 Hz), 4.40(d, 1H, 9.4 Hz), 5.82(dd, 1H, 3.9Hz, 9.6 Hz), 5.89(t, 2H), 6.39(s, 1H), 6.42(s, 2H), 6.49(dd, 1H, 2.0 Hz,9.6 Hz), 6.63(s, 1H).

IR (KBr), νmax, cm⁻¹ : 1726, 1580, 1240, 1125.

EXAMPLE 121,2,3,4-Tetrahydro-6,7-methylenedioxy-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (VIIb) ##STR88##

The tetralone VIb prepared in Example 2 was hydrolyzed according to theprocedure described by W. S. Murphy and S. Wattanasin, J.C.S. Perkin I,271 (1982), and the resulting1,2,3,4-tetrahydro-6,7-methylenedioxy-4-oxo-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (VId) was treated with sodium borohydride according to the generalprocedured described by W. J. Gensler et al., J. Am. Chem. Soc., 82,1714 (1960) to give the title compound as a crystalline solid; m.p.191.5°-193° C. (reported m.p. 181.4°-182° C.).

EXAMPLE 13Trans-1,2-dihydro-6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (VIIIc) ##STR89##

A suspension of alcohol VIIb (400 mg, 0.99 mM) in toluene (20 ml)containing p-toluenesulfonic acid monohydrate (10 mg) was refluxed for 2hours using a Dean-Stark trap. The reaction solution was cooled, washedwith water (15 ml), dried (MgSO₄) and concentrated to a white solid (364mg). Recrytallization and charcoal treatment of solid from methanolafforded the title compound as a crystalline solid; m.p. 177°-180° C.

Anal. Calc'd for C₂₁ H₂₀ O₇ : C, 65.62; H, 5.24. Found: C, 65.61; H,5.26.

¹ H NMR (CDCl₃, δ): 3.60(m, 1H), 3.78(s, 6H), 3.82(s, 3H), 4.40(d, 1H,7.8 Hz), 5.83(dd, 1H, 4.6 Hz, 9.6 Hz), 5.91 (d, 2H), 6.39(s, 2H),6.41(s, 1H), 6.53(dd, 1H, 1.8 Hz, 9.7 Hz), 6.64(s, 1H).

IR (KBr), νmax, cm⁻¹ : 1745, 1710, 1590, 1510, 1485, 1250, 1130.

EXAMPLE 14 Trans-benzhydryl1,2-dihydro-6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIIIa) ##STR90##

A solution of acid VIIIc (1.63 g, 4.24 mM), benzhydryl alcohol (0.79 g,4.29 mM), p-toluenesulfonic acid monohydrate (37 mg) in toluene (100 ml)was refluxed for 2 hours using a Dean-Stark trap. The progress of thereaction was monitored by thin-layer chromatography (2% ethyl acetate inmethylene chloride). The solution was cooled to room temperature andwashed with 5% aqueous sodium bicarbonate solution (90 ml), water (50ml), dried (MgSO₄) and concentrated to a brown oil (2.43 g), which wasfurther purified by column chromatography (silica gel) to afford thetitle compound as a solid amorphous material; m.p. 149°-156° C.

Anal. Calc'd for C₃₄ H₃₀ O₇ : C, 74.17; H, 5.49. Found: C, 74.13; H,5.62.

¹ H NMR (CDCl₃, δ): 3.72(s, 6H), 3.73(m, 1H), 3.83(s, 3H), 4.41(d, 1H,9.6 Hz), 5.84(dd, 1H, 4.2 Hz, 9.6 Hz), 5.89(t, 2H), 6.35(s, 1H), 6.38(s,2H), 6.52(dd, 1H, 2.0 Hz, 9.6 Hz), 6.65(s, 1H), 6.77(s, 1H),7.37-7.07(m, 10H).

EXAMPLE 15dl-8,9-Dihydro-9-(3,4,5-trimethoxyphenyl)-5,8-methano-1,3-dioxolo(4,5-h)(2)benzoxepin-7(5H)-one(5β,8β,9α)(XVa) ##STR91##

A suspension of alcohol VIIb (42.9 g, 0.107 mole) in 1 liter of toluenecontaining p-toluenesulfonic acid monohydrate (500 mg) was heated atreflux temperature for about 2.5 hours using a Dean-Stark trap. Themixture was then treated with 19.6 g (0.107 mole) of benzhydryl alcoholin an additional 100 ml of toluene and refluxed for 3 additional hours.The reaction mixture was washed with 5% aqueous Na₂ CO₃ and a saturatedNaCl solution, dried (MgSO₄) and concentrated to 49.0 g.

The residue was purified by column chromatography over silica gel (350g) using methylene chloride to 5% ethyl acetate in methylene chloride aseluting solvent to yield the title compound. A sample was recrystallizedfrom 95% ethanol with charcoal treatment to yield the title compound asa crystalline solid; m.p. 191.5°-193° C.

Anal. Cal'd for C₂₁ H₂₀ O₇ : C, 65.79; H. 5.26. Found: C, 65.32; H.5.30.

¹ H NMR (CDCl₃, δ): 2.43(m, 2H), 2.98(d, 1H, 5.0 Hz), 3.78 (s, 6H),3.84(s, 3H), 4.40(bs, 1H), 5.25(d, 1H, 4.8 Hz), 5.97(m, 2H), 6.29(s,2H), 6.49(s, 1H), 6.75(s, 1H).

In another experiment, the above procedure was repeated except that thebenzhydryl alcohol utilized therein was omitted from the reaction, andthere was thereby produced the desired lactone XVa.

EXAMPLE 16 Trans-benzhydryl1,2-dihydro-6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(VIIIa) ##STR92##

A mixture of the lactone XVa (3.9 g, 10.2 mM) and benzhydryl alcohol(1.87 g, 10.2 mM) in 100 ml of toluene containing p-toluenesulfonic acidmonohydrate (200 mg) was heated at reflux temperature for about 2.5hours using a Dean-Stark trap. After the theoretical amount of water wascollected (0.2 ml), the reaction mixture was washed with a saturatedNaHCO₃ solution and a saturated NaCl solution, dried (MgSO₄) andconcentrated to an oil, which was further purified by eluting amethylene chloride solution of the oil through a pad of silica gel (15g) with an additional amount of methylene chloride (75 ml). The filtratewas evaporated under reduced pressure to yield 4.06 g of product as anoil. A sample was further purified by column chromatography (alumina)using methylene chloride to 2% ethyl acetate in methylene chloride aseluant to yield the title compound as a solid amorphous material whichwas identical to the product produced in Example 14; m.p. 149°-156° C.

EXAMPLE 17 Cis-ethyl1,2-dihydro-6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(IXb) ##STR93##

To a solution of 1.7M nBuLi in hexane (7.3 ml, 12.4 mM) intetrahydrofuran (20 ml) at -78° C. and under nitrogen was added dropwisediisopropylamine (1.75 ml, 12.5 mM). After stirring for 5 minutes, asolution of trans-olefin VIIIb (2.06 g, 5.0 mM) in tetrahydrofuran (10ml) was added dropwise over a twenty-minute period by a syringe. Afterthe addition was complete, the reaction mixture was warmed to -40° C.over a 30-minute period and stirred at this temperature for 30 minutes.To this stirred solution was added concentrated HCl (2.2 ml) in coldtetrahydrofuran (2.5 ml). The dry-ice acetone bath was removed, and thereaction mixture was warmed to room temperature. Tetrahydrofuran wasremoved under reduced pressure, and the resulting residue waspartitioned between water (100 ml) and methylene chloride (100 ml). Theaqueous layer was further extracted with methylene chloride (50 ml), andthe combined organic extract was washed with water (100 ml), dried(MgSO₄) and concentrated to an oil (2.1 g). This oil was furtherpurified by silica gel column chromatography using 5% ethyl acetate inmethylene chloride as eluting solvent to yield the title compound as anamorphous solid (1.74 g). Recrystallization from ethanol afforded ananalytical sample; m.p. 112°-113° C.

Anal. Calc'd for C₂₃ H₂₄ O₇ : C, 66.98; H, 5.87. Found: C, 66.87; H,5.82.

¹ H NMR (CDCl₃, δ): 1.12(t, 3H, 7.2 Hz), 3.75(s, 6H), 3.76(s, 3H),4.07-3.95(m, 3H), 4.30(d, 1H, 7.7 Hz), 6.11(m, 2H), 6.45(s, 2H),6.50(dd, 1H, 3.0 Hz, 9.7 Hz), 6.61(s, 1H), 6.65(s, 1H).

IR (KBr), νmax, cm⁻¹ : 1730, 1592, 1508, 1490, 1250, 1130.

EXAMPLE 18 Cis-benzhydryl1,2-dihydro-6,7-methylenedioxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(IXc) ##STR94##

The procedure of Example 17 was repeated, except that the trans-olefinVIIIb utilized therein was replaced by the trans-olefin VIIIa, and therewas thereby produced the title compound as a waxy solid.

Anal. Calc'd for C₃₄ H₃₀ O₇ : C, 74.17; H, 5.49. Found: C, 74.17; H,5.76.

¹ H NMR (CDCl₃, δ): 3.51(s, 6H), 3.73(s, 3H), 4.38(dt, 1H, 7.4 Hz, 2.9Hz), 4.38(d, 1H, 7.5 Hz), 5.91(2H), 6.19(dd, 1H, 2.7 Hz, 9.7 Hz),6.40(s, 2H), 6.51(dd, 1H, 2.9 Hz, 9.8 Hz), 6.65(s, 2H), 6.75(s, 1H),7.11-7.37(m, 10H).

EXAMPLE 19dl-8,9-Dihydro-9-(3,4,5-trimethoxyphenyl)-5,8-methano-1,3-dioxolo(4,5-h)(2)benzoxepin-7(5H)-one(5α,8α,9α)(XVIIIa) ##STR95##

To a solution of the cis-aryltetralone XVIb (124 mg, 0.29 mM) in 10 mlof dry tetrahydrofuran was added 0.29 ml of 2.0M LiBH₄ intetrahydrofuran (0.58 mM). After stirring at room temperature for 17hours, the reaction mixture was treated with 7 ml of a saturated NH₄ Clsolution and the solvent layers were separated. The aqueous layer wasfurther extracted with ether (3×5 ml), and the combined organic extractwas dried (MgSO₄) and concentrated to a light yellow oil. This oil wasfurther purified by preparative thin-layer chromatography using 5%methanol in methylene chloride as eluting solvent. The appropriatefraction at about R_(f) =0.53 was collected, filtered and concentratedto yield the title compound as an oil; TLC [silica/methanol:methylenechloride (5:95)] gave R_(f) =0.53.

¹ H NMR (CDCl₃, δ): 2.33(d, 1H, 11.5 Hz), 2.82(m, 1H), 3.03(t, 1H, 4.9Hz), 3.79(s, 6H), 3.85(s, 3H), 4.36(d, 1H, 4.5 Hz), 5.24(d, 1H, 5.2 Hz),5.94(bd, 2H), 6.30(s, 2H), 6.48(s, 1H), 6.75(s, 1H).

EXAMPLE 20 dl-[3aβ,4α,5α,10bβ]-Ethyl3a,4,5,10b-tetrahydro-3-bromo-5-(3,4,5-trimethoxyphenyl)-1,3-dioxolo(6,7)naph(2,1-d)isoxazole-4-carboxylate(Xa) ##STR96## A. Dibromoformaldoxime

To glyoxylic acid oxime hydrate (12 g, 112 mM) in water (60 ml) wasadded under stirring and ice bath temperature (0°-4° C.) methylenechloride (130 ml) and sodium bicarbonate (18.83 g, 224 mM). To thistwo-phase mixture was added bromine (35.84 g, 488 mmoles) in methylenechloride (50 ml), and stirring was continued for 7 hours (at 0° C.)followed by additional stirring at room temperature for 13 hours. Excessbromine was destroyed by careful addition of solid sodium thiosulfate.The organic layer was separated and the aqueous layer further extractedwith methylene chloride (2×100 ml). The combined organic extract wasdried (Na₂ SO₄) and evaporated to afford the title product as a whitesolid (11.4 g, 50.13% yield). A portion of this material wasrecrystallized from Skellysolve B to obtain an analytical sample; m.p.65°-68° C.

IR (KBr): 3000-3600, 1580 and 980 cm⁻¹.

Anal. Calc'd for CHNOBr₂ : C, 5.91; H, 0.49; N, 6.90. Found: C, 5.40; H,0.20; N, 6.95.

B. dl-[3aβ,4α,5α,10bβ]-Ethyl3a,4,5,10b-tetrahydro-3-bromo-5-(3,4,5-trimethoxyphenyl)-1,3-dioxolo(6,7)napth(2,1-d)-isoxazole-4-carboxylate(Xa)

To a solution of cis-olefin IXb (0.10 g, 0.24 mM) in acetone was addeddibromoformaldoxime (146 mg, 0.72 mM) [prepared in Step A] followed byKHCO₃ (145 mg, 1.45 mM). The solution was refluxed at 56° C. for 3hours. Thin-layer chromatography [ether:Skellysolve B (1:1)] indicatedthat almost all of the starting material (R_(f) =0.30) was consumed andthe product spot at R_(f) =0.19 had appeared. The solution was cooled,the solids were filtered off and washed with methylene chloride. Thefiltrate was concentrated to a yellow oily solid. Pure product (72 mg)was obtained by silica gel column chromatography using 4% ethyl acetatein methylene chloride as the eluting solvent. Recrystallization fromethanol afforded the title compound as a crystalline solid; m.p.212°-214° C. (dec.).

Anal. Calc'd for C₂₄ H₂₄ NO₈ Br: C, 53.95; H, 4.53; N, 2.62. Found: C,53.64; H, 4.52; N, 2.91.

¹ H NMR (CDCl₃, δ): 1.19(t, 3H, 7.2 Hz), 3.14(dd, 1H, 4.9 Hz, 10.7 Hz),3.76(s, 6H), 3.81(s, 3H), 3.93(t, 1H, 10.3 Hz), 4.10(q, 2H), 4.37(d, 1H,4.9 Hz), 5.71(d, 1H, 9.7 Hz), 5.98(s, 2H), 6.08(s, 2H), 6.57(s, 1H),7.02(s, 1H).

IR (KBr), νmax, cm⁻¹ : 1732, 1590, 1495, 1482, 1235, 1120.

EXAMPLE 21 dl-[3aβ,4α,5α,10bβ]-Benzhydryl3a,4,5,10b-tetrahydro-3-bromo-5-(3,4,5-trimethoxyphenyl)-1,3-dioxolo(6,7)napth(2,1-d)isoxazole-4-carboxylate(Xb) ##STR97##

To a solution of cis-olefin IXc (0.85 g, 1.54 mM) in ethyl acetate (40ml) was added dibromoformaldoxime (0.94 g, 4.63 mM), followed by KHCO₃(0.47 g, 4.69 mM). The suspension was refluxed for 3 hours. Thin-layerchromatography [ether:Skelly-solve B (1:1)] revealed that the reactionwas approximately 60% complete. Consequently, additionaldibromoformaldoxime (0.47 g) and KHCO₃ (0.24 g) were added to thereaction mixture, and the solution was further refluxed for 2.5 hours.The solution was cooled and concentrated to an oil, which waspartitioned between methylene chloride and water. The aqueous layer wasfurther extracted with methylene chloride, and the combined organicextract was dried (MgSO₄) and concentrated to an oil. The title compound(0.61 g, R_(f) =0.25) was obtained as a solid by silica gel columnchromatography of the above oil using 1-3% ethyl acetate in methylenechloride as eluting solvent. An analytical sample was obtained bytrituration with ethanol; m.p. 164.5°- 168° C.

Anal. Calc'd for C₃₅ H₃₀ NO₈ Br: C, 62.50; H, 4.50; N, 2.08; Br, 11.88.Found: C, 62.12; H, 4.45; N, 2.08; Br, 10.75.

¹ H NMR (CDCl₃, δ): 3.30(dd, 1H, 4.7 Hz, 9.4 Hz), 3.44(s, 6H), 3.76(s,3H), 3.96(t, 1H, 9.7 Hz), 4.34(d, 1H, 4.7 Hz), 5.69(d, 1H, 10.1 Hz),5.95(s, 2H), 5.98(d, 2H), 6.57(s, 1H), 6.93(s, 1H), 7.01(s, 1H),7.39-7.12(m, 10H).

IR (KBr), νmax, cm⁻¹ : 1750, 1590, 1502, 1483, 1240, 1130.

EXAMPLE 22 dl-[3aα,4β,5α,10bα]-Ethyl3a,4,5,10b-tetrahydro-3-bromo-5-(3,4,5-trimethoxyphenyl)-1,3-dioxolo(6,7)napth(2,1-d)isoxazole-4-carboxylate(XXI) ##STR98##

To a solution of trans-olefin VIIIb (100 mg, 0.24 mM) in ethyl acetate(5 ml) was added dibromoformaldoxime (148 mg, 0.73 mM), followed byKHCO₃ (145 mg, 1.45 mM) and water (2 drops). The reaction mixture wasstirred at room temperature for 18 hours. Thin-layer chromatography (5%ethyl acetate in methylene chloride) revealed that all of the startingmaterial (R_(f) =0.71) was consumed and two new spots at R_(f) 's=0.57and 0.90 had appeared. The reaction mixture was filtered, and the solidprecipitates were washed with ethyl acetate. The filtrate was dried(MgSO₄) and concentrated to a solid residue. The desired product (R_(f)=0.57) was obtained by silica gel column chromatography using methylenechloride and 10% ethyl acetate in methylene chloride as elutingsolvents, as an amorphous solid (80 mg); m.p. 208°-209° C. (dec.). Ananalytical sample of the title compound was obtained byrecrystallization from 95% ethanol; m.p. 212°-214° C. (dec.).

Anal. Calc'd for C₂₄ H₂₄ NO₈ Br: C, 53.95; H, 4.53; N, 2.62. Found: C,53.95; H, 4.48; N, 2.58.

¹ H NMR (CDCl₃, δ): 1.04(t, 3H, 7.2 Hz), 3.12(t, 1H, 8.1 Hz), 3.80(s,6H), 3.84(s, 3H), 4.08-3.92(m, 3H) 4.17(d, 1H, 8.1 Hz), 5.62(d, 1H, 10.1Hz), 5.97(s, 2H), 6.31(s, 2H), 6.37(s, 1H), 6.95(s, 1H).

IR (KBr), νmax, cm⁻¹ : 1735, 1585, 1498, 1480, 1245, 1120.

EXAMPLE 23dl-[3aβ,4α,5α,10bβ]-3a,4,5,10b-tetrahydro-3-chloro-5-(3,4,5-trimethoxyphenyl)-1,3-dioxolo(6,7)napth(2,1-d)isoxazole-4-carboxylicacid (Xc) ##STR99##

To a solution of ester Xb (0.41 g, 0.61 mM) in nitromethane (12 ml) wasadded at room temperature 1N HCl (3.5 ml in nitromethane). The solutionwas stirred at room temperature for 3 hours and at ice-bath temperaturefor 30 minutes. The cold solution was filtered to collect the titlecompound as a white crystalline solid (175 mg); m.p. 238.5° C.

Anal. Calc'd for C₂₂ H₂₀ NO₈ Cl: C, 57.21; H, 4.36; N, 3.03. Found: C,57.13; H, 4.39; N, 3.18.

¹ H NMR (CDCl₃, δ): 3.24(dd, 1H, 4.9 Hz, 11.0 Hz), 3.74(s, 6H), 3.80(s,3H), 3.86(t, 1H, 10.7 Hz), 4.42(d, 1H, 4.7 Hz), 5.76(d, 1H, 9.8 Hz),5.98(s, 2H), 6.12(s, 2H), 6.58(s, 1H), 7.02(s, 1H).

IR (KBr), νmax, cm⁻¹ : 2800-3100, 1715, 1520, 1485, 1230, 1125, 1035.

EXAMPLE 24dl-[3aβ,4α,5α,10bβ]-3a,4,5,10b-tetrahydro-3-bromo-5-(3,4,5-trimethoxyphenyl)-1,3-dioxolo(6,7)napth(2,1-d)isoxazole-4-carboxylicacid (Xd) ##STR100##

A cold (0° C.) solution of the ester Xb (134 mg, 0.2 mM) in 1.3 ml oftrifluoroacetic acid was allowed to warm to room temperature. After 2hours of stirring, the trifluoroacetic acid was removed under reducedpressure at about 35° C. The residue was treated with water and filteredto yield the title compound. A portion of the solid was purified bysilica gel chromatography using 10% methanol in methylene chloride asthe eluting solvent to afford the title compound (42 mg) as acrystalline solid; m.p. 225°-229° C.

EXAMPLE 25dl-[1α,2α,3β,4β]-1,2,3,4-Tetrahydro-3-cyano-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (XIg) ##STR101##

To a suspension of chloroisoxazoline acid Xc (2.00 g, 0.43 mM) inmethanol (100 ml) was added Raney nickel (about 0.5 cc), and thesuspension was shaken on a Parr apparatus under 42 psi hydrogen pressurefor 4 hours. Platinum oxide (50 mg) was added to the solution andshaking continued on the hydrogenator for an additional 2.5 hours. Thecatalysts were filtered off through a diatomaceous earth pad and thefiltrate concentrated to a solid residue (2 g). Thin-layerchromatography (20% methanol in methylene chloride) of the solid residuerevealed besides the starting acid (R_(f) =0.53) two additionalcomponents at R_(f) =0.30 (major) and R_(f) =0.09 (minor). The majorcomponent at R_(f) =0.30 was isolated as a white solid (0.9 g) by silicagel column chromatography using methanol-methylene chloride (1:5) aseluting solvent. Recrytallization from methanol afforded an analyticalsample of the title compound; m.p. 245°-246.5° C. (dec.).

Anal. Calc'd for C₂₂ H₂₁ NO₈ : C, 61.82; H, 4.95; N, 3.28. Found: C,61.67; H, 4.94; N, 3.27.

¹ H (CDCl₃, δ): 3.35(dd, 3.4 Hz, 12.4 Hz), 3.71(dd, 1H, 12.5 Hz, 5.8Hz), 3.74(s, 6H), 3.78(s, 3H), 4.55(d, 1H, 5.7 Hz), 4.98(d, 1H, 3.2 Hz),5.94(m, 2H), 6.11(s, 2H), 6.41(s, 1H), 6.86(s, 1H).

IR (KBr), νmax, cm⁻¹ : 3490, 2920, 2240, 1750, 1590, 1500, 1485, 1240,1130, 1035.

EXAMPLE 26dl-[1α,2α,3β,4β]-1,2,3,4-Tetrahydro-3-cyano-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (XIg) ##STR102##

Raney nickel (about 1.0 cc) was added to a suspension ofchloroisoxazoline acid Xc (1.40 g, 3.23 mM) in methanol (200 ml), andthe suspension was hydrogenated on a Parr apparatus under an initialhydrogen pressure of 50 psi for 2 hours. The catalyst was filtered offthrough diatomaceous earth and the solvent evaporated under reducedpressure. The aqueous solution was acidified with 6N HCl and extractedwith 10% methanol in methylene chloride. The combined organic extractwas dried (MgSO₄) and evaporated to yield the title compound as anamorphous solid (0.8 g, 60%), whose ¹ H NMR spectrum was identical tothe product produced in Example 25.

EXAMPLE 27 dl-[1α,2α,3β,4β]-Ethyl1,2,3,4-tetrahydro-3-cyano-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(XIh) ##STR103##

To a suspension of ester Xa (0.106 g, 0.2 mM) in ethyl acetate saturatedwith water (20 ml) and methanol (5 ml) was added boric acid (36 mg, 0.6mM) followed by Raney nickel (about 0.1 cc). The suspension washydrogenated in a Parr apparatus at 40 psi for 6 hours. Thin-layerchromatography (5% ethyl acetate in methylene chloride) revealed,besides the starting ester Xa (R_(f) =0.61), a new component at R_(f)=0.15. The catalyst was filtered off, and the filtrate was concentratedto a solid residue. Silica gel column chromatography of this residue,using 5% and 10% ethyl acetate in methylene chloride as elutingsolvents, affording the title compound (R_(f) =0.15) as an amorphoussolid (54 mg). Recrystallization from 95% ethanol afforded the titlecompound; m.p. 215°-216° C.

Anal. Calc'd for C₂₄ H₂₅ NO₈ : C, 63.29; H, 5.53; N, 3.08. Found: C,63.16; H, 5.59; N, 3.02.

¹ H NMR (CDCl₃, δ): 1.17(t, 3H, 7.3 Hz), 2.62(d, 1H, 4.4 Hz), 3.44(dd,1H, 3.3 Hz, 12.4 Hz), 3.74(m, 1H), 3.74(s, 6H), 3.80(s, 3H), 4.06(q, 2H,7.1 Hz), 4.53(d, 1H, 5.9 Hz), 5.07(t, 1H, 3.8 Hz), 5.97(dd, 2H), 6.03(s,2H), 6.42(s, 1H), 6.85(s, 1H).

IR (KBr), νmax, cm⁻¹ : 3560, 2245, 1725, 1590, 1235, 1128.

EXAMPLE 28 dl-[1α,2α,3β,4β]-Ethyl1,2,3,4-tetrahydro-3-cyano-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(Xih) ##STR104##

A solution of ester Xa (64 mg, 0.12 mM) in 5 ml of dry benzene under anitrogen atmosphere was treated with tributyltin hydride (0.12 ml, 0.45mM) and 2,2'-azobisisobutyronitrile (2 mg). The mixture was heated atreflux temperature for 6 hours and then stirred at room temperatureovernight. The reaction mixture was evaporated under reduced pressureand the residue was purified by silica gel column chromatography using5% and 15% ethyl acetate in methylene chloride as eluting solvent. Theappropriate fractions were combined and evaporated under reducedpressure to give the title compound, whose ¹ H NMR spectrum wasidentical to the product produced in Example 27.

EXAMPLE 29 dl-[1α,2α,3β,4β]-Ethyl1,2,3,4-tetrahydro-3-cyano-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylate(XIh) ##STR105##

A suspension of ester Xa (106 mg, 0.2 mM) in 10 ml of 90% aqueousmethanol containing 0.08 ml of concentrated HCl and 10 mg of 10% Pd/C(55% by weight in water) was hydrogenated under a hydrogen pressure of 1atmosphere for 24 hours and then allowed to stand for 5 days. Thecatalyst was filtered off through diatomaceous earth and the solutionwas neutralized to about pH 7 with saturated NaHCO₃ solution before thesolvent was evaporated under reduced pressure. The residue was purifiedby silica gel column chromatography using 20% ethyl acetate in methylenechloride as eluting solvent to give 40 mg of the title compound, whichwas identical to the product produced in Example 27.

EXAMPLE 30dl-[1α,2α,3β,4β]-1,2,3,4-Tetrahydro-3-cyano-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (XIg) ##STR106##

To a solution of chloroisoxazoline acid Xc (92 mg, 0.2 mM) in 50 ml ofsolvent (comprising 36 ml of methanol, 10 ml of methylene chloride and 4ml of water) was added 30 mg of nickel boride, and the mixture washydrogenated on a Parr apparatus under an initial hydrogen pressure of40 psi for 16 hours. The catalyst was filtered off through diatomaceousearth and the solvent evaporated under reduced pressure to yield 90 mgof the title compound, which was identical to the product produced inExample 25.

EXAMPLE 31dl-[1α,2α,3β,4β]-1,2,3,4-Tetrahydro-3-aminomethyl-4-hydroxy-1-(3,4,5-trimethoxyphenyl)naphthalene-2-carboxylicacid (XIi) ##STR107##

A solution of the hydroxynitrile XIg (0.50 g, 1.2 mM) in drytetrahydrofuran (15 ml) was added under nitrogen at 0° C. to a stirredsuspension of lithium aluminum hydride (0.16 g, 4.2 mM) intetrahydrofuran (20 ml). After 16 hours at room temperature, the excesslithium aluminum hydride was decomposed by sequential addition of water(0.16 ml), 15% sodium hydroxide solution (0.16 ml) and water (0.48 ml).The precipitate was filtered off and the tetrahydrofuran was removedunder reduced pressure. The aqueous solution was acidified to pH 6 with0.1N HCl and extracted with methylene chloride. The combined extract wasdried (MgSO₄) and evaporated to yield the title compound (0.12 g, 24%).A portion of this sample was dissolved in methanol-methylene chloride(1:4) and applied to a solid phase extraction cartridge of silica. Thecolumn was washed with methanol (4 ml) and the amino acid eluted with10% acetic acid in methanol (2 ml). The solvent was evaporated and theresulting solid dried under high vacuum at 78° C. to give the titlecompound as an acetic acid salt.

Anal. Calc'd for C₂₂ H₂₅ NO₈ CH₃ COOH.H₂ O: C, 56.57; H, 6.13; N, 2.75.Found: C, 56.85; H, 6.28; N, 2.68.

¹ H NMR (CDCl₃, δ): 6.84(s, 1H), 6.32(s, 1H), 6.05(s, 2H), 5.88 (d, 2H),4.86(bp, 1H), 4.10(bp, 1H), 3.79(s, 3H), 3.73(s, 6H), 3.26(bp, 2H),3.13(m, 1H), 2.60(m, 1H), 2.30(m, 1H).

EXAMPLE 32 dl-Epipodophyllotoxin (I) ##STR108##

To a solution of chloroisoxazoline acid Xc (200 mg, 0.43 mM) in 100 mlof CH₃ OH/H₂ O/CH₂ Cl₂ (7:1:3) was added nickel boride (60 mg, 0.86 mM),and the suspension was subjected to hydrogenation in a Parr apparatus at40 psi hydrogen pressure for 18 hours. Platinum oxide (200 mg, 0.88 mM)was added to the solution, and the suspension was further hydrogenatedat 40 psi for 2 hours. Thin-layer chromatography (5% MeOH in CH₂ Cl₂)indicated the disappearance of the starting acid (R_(f) =0.48) and theappearance of a highly polar component (R_(f) =0.07). The catalysts werefiltered off on a diatomaceous earth pad, and the filtrate wasconcentrated to a syrup. The syrup was dissolved in 50% acetic acid (7ml), and to the resulting solution was added sodium nitrite (200 mg, 2.9mM) solution in water (8 ml). After stirring the solution at roomtemperature for 4 hours, saturated aqueous sodium bicarbonate solution(20 ml) was carefully added, and the reaction solution was extractedwith methylene chloride (5×30 ml). The combined organic extract wasdried (Na₂ SO₄), filtered and concentrated to give the title compound asa light yellow solid (84 mg) which was homogeneous on thin-layerchromatography.

¹ H NMR (CDCl₃, δ): 2.86(m, 1H), 3.29(dd, 1H, 5.1 Hz, 14.1 Hz), 3.75(s,6H), 3.81(s, 3H), 4.38(m, 2H), 4.63(d, 1H, 5.1 Hz), 4.88(t, 1H, 3.4 Hz),6.00(d, 2H), 6.29(s, 2H), 6.56(s, 1H), 6.89(s, 1H).

The above spectral data is in agreement with the data forepipodophyllotoxin reported in J. Med. Chem. 22, 215 (1979).

EXAMPLE 33 dl-Epipodophyllotoxin (I) ##STR109##

A solution of the hydroxynitrile XIg (0.25 g, 0.59 mM) in drytetrahydrofuran (7 ml) was added under nitrogen to a cooled solution oflithium aluminum hydride (0.08 g, 2 mM) in tetrahydrofuran (20 ml). Thereaction mixture was stirred for 16 hours at room temperature. Thereaction was terminated by adding 1:1 (v/v) acetic acid in water (10ml), and the tetrahydrofuran was removed under reduced pressure. Asolution of sodium nitrite (200 mg, 2.9 mM) in water (1 ml) was added tothe residue and stirred at room temperature for 1 hour. Saturatedaqueous NaHCO₃ solution was added to neutralize the acidic solution, andthe mixture was then extracted with methylene chloride. The combinedorganic extract was dried (MgSO₄) and evaporated to yieldepipodophyllotoxin (I) (0.21 g, 87%) as a light-brown foam; the ¹ H NMRspectrum was identical to the epipodophyllotoxin prepared in Example 32.

EXAMPLE 34

When the general procedure of Examples 1, 2, 10, 11, 17, 20, 23 and 32are sequentially repeated, except that the starting material3,4,5-trimethoxy-3',4'-methylenedioxy chalcone XXIIa utilized in Example1 is replaced by an equimolar amount of a compound of the formula

    ______________________________________                                         ##STR110##              XXIIb-XXIIg                                          wherein                                                                       Compound                                                                              R.sup.1 R.sup.2 R.sup.4                                                                             R.sup.5                                                                            R.sup.6                                    ______________________________________                                        XXIIb   H       OCH.sub.3                                                                             H     CH.sub.3                                                                           H                                          XXIIc   H       OCH.sub.3                                                                             OCH.sub.3                                                                           CH.sub.3                                                                           H                                          XXIId   OCH.sub.3                                                                             OCH.sub.3                                                                             H     CH.sub.3                                                                           H                                          XXIIe   OCH.sub.3                                                                             OCH.sub.3                                                                             OCH.sub.3                                                                           CH.sub.3                                                                           H                                          XXIIf   OCH.sub.2 O OCH.sub.3                                                                             CH.sub.3                                                                           H    and                                     XXIIg   OCH.sub.3                                                                             H       H     CH.sub.3                                                                           H,   respectively                          ______________________________________                                    

[which are prepared by the general procedures described in Synthesis,647-650 (1980)], there is thereby produced a compound of the formula

    ______________________________________                                         ##STR111##                XIIb-XIIb                                          wherein                                                                       Compound                                                                              R.sup.1 R.sup.2 R.sup.4                                                                             R.sup.5                                                                            R.sup.6                                    ______________________________________                                        XIIb    H       OCH.sub.3                                                                             H     CH.sub.3                                                                           H                                          XIIc    H       OCH.sub.3                                                                             OCH.sub.3                                                                           CH.sub.3                                                                           H                                          XIId    OCH.sub.3                                                                             OCH.sub.3                                                                             H     CH.sub.3                                                                           H                                          XIIe    OCH.sub.3                                                                             OCH.sub.3                                                                             OCH.sub.3                                                                           CH.sub.3                                                                           H                                          XIIf    OCH.sub.2 O OCH.sub.3                                                                             CH.sub.3                                                                           H    and                                     XIIg    OCH.sub.3                                                                             H       H     CH.sub.3                                                                           H,   respectively                          ______________________________________                                    

We claim:
 1. A compound of the formula ##STR112## wherein R¹ and R² eachare independently hydrogen or (lower)alkoxy, or R¹ and R², takentogether, is methylenedioxy;R³ is hydrogen or a carboxyl-protectinggroup; R⁴ and R⁶ each are independently hydrogen or (lower)alkoxy; R⁵ ishydrogen or a phenol-protecting group; and R⁷ is hydrogen, halogen,(lower)alkoxycarbonyl, carboxyl, cyano, trimethylsilyl, phenylsulfonylor phenoxycarbonyl in which the phenyl ring of R⁷ may have one or twosubstituents independently selected from (lower)alkyl, halogen,(lower)alkoxy and trifluoromethyl; or an acid addition salt thereof. 2.A compound of claim 1 having the formula ##STR113## wherein R³ ishydrogen or a carboxyl-protecting group;R⁵ is hydrogen or aphenol-protecting group; and R⁷ is hydrogen, halogen,(lower)alkoxycarbonyl, carboxyl, cyano, trimethylsilyl, phenylsulfonylor phenoxycarbonyl in which the phenyl ring of R⁷ may have one or twosubstituents independently selected from (lower)alkyl, halogen,(lower)alkoxy and trifluoromethyl; or an acid addition salt thereof. 3.A compound of claim 2 wherein R³ is hydrogen, (lower)alkyl,phenyl(lower)alkyl, ring substituted phenyl(lower)alkyl ordiphenylmethyl; R⁵ is hydrogen, (lower)alkyl, phenyl(lower)alkyl, ringsubstituted phenyl(lower)alkyl, benzyloxycarbonyl or2,2,2-trichloroethoxycarbonyl; and R⁷ is halogen, (lower)alkoxycarbonyl,trimethylsilyl, phenylsulfonyl or phenoxycarbonyl; in which the phenylring of R³, R⁵ and R⁷ may have one or two substituents independentlyselected from (lower)alkyl, halogen, (lower)alkoxy and trifluoromethyl;or an acid addition salt thereof.
 4. The compound of claim 3 wherein R³is diphenylmethyl; R⁵ is methyl; and R⁷ is bromine.
 5. The compound ofclaim 3 wherein R³ is hydrogen; R⁵ is methyl; and R⁷ is chlorine; or anacid addition salt thereof.
 6. The compound of claim 3 wherein R³ isethyl; R⁵ is methyl; and R⁷ is bromine.
 7. The compound of claim 3wherein R³ is hydrogen; R⁵ is methyl; and R⁷ is bromine; or an acidaddition salt thereof.